As filed with the U.S. Securities and Exchange Commission on February 16, 2024

Securities Act File No. 333-191151
Investment Company Act File No. 811-22887

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER THE SECURITIES ACT OF 1933	¨
Pre-Effective Amendment No.	¨
Post-Effective Amendment No. 28	x

and/or

REGISTRATION STATEMENT

UNDER THE INVESTMENT COMPANY ACT OF 1940 ¨

Amendment No. 30 x

(Check appropriate box or boxes)

Calamos ETF Trust

(Exact Name of Registrant as Specified in Charter)

2020 Calamos Court
Naperville, Illinois
(Address of Principal Executive Offices)

60563
(Zip Code)

Registrant’s Telephone Number, including Area Code: (630) 245-7200

Erik D. Ojala

2020 Calamos Court

Naperville, Illinois 60563

(Name and Address of Agent for Service)

With Copies to:

Paulita A. Pike and Rita Rubin
Ropes & Gray LLP
191 North Wacker Drive, 32nd Floor
Chicago, Illinois 60606

Approximate Date of Proposed Public Offering: As soon as practicable following the effectiveness of the Registration Statement.

It is proposed that this filing will become effective:

x  immediately upon filing pursuant to paragraph (b)

¨  on [ ] pursuant to paragraph (b)

¨  60 days after filing pursuant to paragraph (a)(1)

¨  on [ ] pursuant to paragraph (a)(1)

¨  75 days after filing pursuant to paragraph (a)(2)

¨  on pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

¨  This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

CALAMOS ETF TRUST

CONTENTS OF POST EFFECTIVE AMENDMENT NO. 28

This Registration Statement consists of the following papers and documents:

Cover Sheet

Explanatory Note

*Part A – Prospectus

*Part B – Statement of Additional Information

Part C – Other Information

Signature Page

*Incorporated by reference from the Post-Effective Amendment No. 25 to Registrant’s Registration Statement on Form N-1A, filed on February 7, 2024.

Explanatory Note

Post-Effective Amendment No. 25 to the Registration Statement on Form N-1A (File No. 333-191151) (the “Registration Statement”) of Calamos ETF Trust (the “Registrant”) was filed on February 7, 2024, pursuant to Rule 485(b) under the Securities Act of 1933, as amended (the “Securities Act”).

This Post-Effective Amendment No. 28 is being filed solely for the purpose of refiling the signature page that was included with Post-Effective Amendment No. 25. This Post-Effective Amendment No. 28 does not modify any other part of the Registration Statement. The contents of Part A and Part B of Post-Effective Amendment No. 25 are incorporated herein by reference.

PART C

OTHER INFORMATION

Item 28. EXHIBITS.

(a)	(i)	Amended and Restated Certificate of Trust of the Registrant (incorporated by reference to Exhibit (a)(ii) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(ii)	Second Amended and Restated Trust Instrument (incorporated by reference to Exhibit (a)(iii) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
(b)		Bylaws of the Registrant (incorporated by reference to Exhibit (b) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
(c)		See Articles IV, V, and VI of Exhibit (a)(iii) above and Article V of Exhibit (b) above.
(d)	(i)	Investment Advisory Agreement dated January 10, 2023 by and between Calamos ETF Trust and Calamos Antetokounmpo Asset Management LLC (incorporated by reference to Exhibit (d)(i) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(ii)	Sub-Advisory Agreement dated January 10, 2023 by and among Calamos Antetokounmpo Asset Management LLC, Calamos Advisors LLC and Calamos ETF Trust (incorporated by reference to Exhibit (d)(ii) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(iii)	Investment Advisory Agreement dated September 1, 2023 by and between Calamos ETF Trust and Calamos Advisors LLC (incorporated by reference to Exhibit (d)(iii) to Post-Effective Amendment No. 16 to Registrant’s Registration Statement on Form N-1A, filed on September 28, 2023).
	(iv)	Amendment, dated September 26, 2023, regarding Calamos CEF Income & Arbitrage ETF, to Investment Advisory Agreement by and between Calamos ETF Trust and Calamos Advisors LLC (incorporated by reference to Exhibit (d)(iv) to Post-Effective Amendment No. 18 to Registrant’s Registration Statement on Form N-1A, filed on November 21, 2023).
	(v)	Amendment, dated December 12, 2023, regarding Calamos Alternative Nasdaq & Bond ETF, to Investment Advisory Agreement by and between Calamos ETF Trust and Calamos Advisors LLC (incorporated by reference to Exhibit (d)(v) to Post-Effective Amendment No. 22 to Registrant’s Registration Statement on Form N-1A, filed on January 10, 2024).
(e)	(i)	Distribution Agreement dated December 16, 2022 (incorporated by reference to Exhibit (e) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(ii)	First Amendment to Distribution Agreement, effective September 1, 2023 (incorporated by reference to Exhibit (e)(ii) to Post-Effective Amendment No. 16 to Registrant’s Registration Statement on Form N-1A, filed on September 28, 2023).
	(iii)	Second Amendment to Distribution Agreement, effective September 26, 2023 (incorporated by reference to Exhibit (e)(iii) to Post-Effective Amendment No. 18 to Registrant’s Registration Statement on Form N-1A, filed on November 21, 2023).
	(iv)	ETF Distribution Agreement dated December 19, 2023 between Calamos ETF Trust and Calamos Financial Services LLC (incorporated by reference to Exhibit (e)(iv) to Post-Effective Amendment No. 22 to Registrant’s Registration Statement on Form N-1A, filed on January 10, 2024).
(f)	Not applicable.
(g)	(i)	Master Custodian Agreement with State Street Bank and Trust Company, dated September 11, 2009 (incorporated by reference to Exhibit (g)(i) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(ii)	Notification of Additional Fund, dated December 21, 2022, pursuant to Master Custodian Agreement (incorporated by reference to Exhibit (g)(ii) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(iii)	Notification of Additional Funds, dated September 26, 2023, pursuant to Master Custodian Agreement (incorporated by reference to Exhibit (g)(iii) to Post-Effective Amendment No. 17 to Registrant’s Registration Statement on Form N-1A, filed on October 6, 2023).

	(iv)	Notification of Additional Fund, dated December 12, 2023, pursuant to Master Custodian Agreement (incorporated by reference to Exhibit (g)(iv) to Post-Effective Amendment No. 22 to Registrant’s Registration Statement on Form N-1A, filed on January 10, 2024).
(h)	Other Material Contracts.
	(i)	Transfer Agency and Service Agreement, with State Street Bank and Trust Company dated as of March 21, 2014 (incorporated by reference to Exhibit (h)(2) to Pre-Effective Amendment No. 1 to Registrant’s Registration Statement on Form N-1A, filed on May 28, 2014).
	(ii)	Notification of Additional Fund, dated December 21, 2022, pursuant to Transfer Agency and Service Agreement (incorporated by reference to Exhibit (h)(ii) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(iii)	Notification of Additional Funds, dated September 26, 2023, pursuant to Transfer Agency and Service Agreement (incorporated by reference to Exhibit (h)(iii) to Post-Effective Amendment No. 17 to Registrant’s Registration Statement on Form N-1A, filed on October 6, 2023).
	(iv)	Notification of Additional Fund, dated December 12, 2023, pursuant to Transfer Agency and Service Agreement (incorporated by reference to Exhibit (h)(iv) to Post-Effective Amendment No. 22 to Registrant’s Registration Statement on Form N-1A, filed on January 10, 2024).
	(v)	Administration Agreement, effective November 1, 2018 with State Street Bank (incorporated by reference to Exhibit (h)(iii) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(vi)	Notification of Additional Fund, dated December 21, 2022, pursuant to Administration Agreement (incorporated by reference to Exhibit (h)(iv) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(vii)	Notification of Additional Funds, dated October 3, 2023, pursuant to Administration Agreement (incorporated by reference to Exhibit (h)(vi) to Post-Effective Amendment No. 17 to Registrant’s Registration Statement on Form N-1A, filed on October 6, 2023).

	(viii)	Amendment to Administration Agreement, dated January 4, 2024 (incorporated by reference to Exhibit (h)(viii) to Post-Effective Amendment No. 25 to Registrant’s Registration Statement on Form N-1A, filed on February 7, 2024).
	(ix)	Master Services Agreement, dated March 15, 2004, with State Street Bank and Trust Company (incorporated by reference to Exhibit (h)(v) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(x)	Notification of Additional Funds, dated December 21, 2022, pursuant to the Master Services Agreement (incorporated by reference to Exhibit (h)(vi) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(xi)	Notification of Additional Funds, dated September 26, 2023, pursuant to the Master Services Agreement (incorporated by reference to Exhibit (h)(ix) to Post-Effective Amendment No. 17 to Registrant’s Registration Statement on Form N-1A, filed on October 6, 2023).
	(xii)	Notification of Additional Fund, dated December 12, 2023, pursuant to the Master Services Agreement (incorporated by reference to Exhibit (h)(xii) to Post-Effective Amendment No. 22 to Registrant’s Registration Statement on Form N-1A, filed on January 10, 2024).
	(xiii)	Form of Authorized Participant Agreement (incorporated by reference to Exhibit (h)(vii) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(xiv)	Revised Form of Authorized Participant Agreement (incorporated by reference to Exhibit (h)(xiii) to Post-Effective Amendment No. 22 to Registrant’s Registration Statement on Form N-1A, filed on January 10, 2024).
(i)	Legal Opinion and Consent (incorporated by reference to Exhibit (i) to Post-Effective Amendment No. 25 to Registrant’s Registration Statement on Form N-1A, filed on February 7, 2024).
(j)	Not applicable.
(k)	Not applicable.
(l)	Not applicable.
(m)	Rule 12b-1 Plan (incorporated by reference to Exhibit (m) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(i) Amendment to Rule 12b-1 Plan dated September 26, 2023 (incorporated by reference to Exhibit (m)(i) to Post-Effective Amendment No. 16 to Registrant’s Registration Statement on Form N-1A, filed on September 28, 2023).
	(ii) Amendment to Rule 12b-1 Plan dated December 12, 2023 (incorporated by reference to Exhibit (m)(ii) to Post-Effective Amendment No. 22 to Registrant’s Registration Statement on Form N-1A, filed on January 10, 2024).
(n)	Not applicable.
(o)	Not applicable.
(p)	Code of Ethics.
	(i)	Code of Ethics of CGAM, LLC (incorporated by reference to Exhibit (p)(i) to Post-Effective Amendment No. 10 to Registrant’s Registration Statement on Form N-1A, filed on January 23, 2023).
	(ii)	Code of Ethics and Insider Trading Policy of Registrant, Calamos Advisors LLC, Calamos Financial Services LLC and certain affiliated entities, dated December 12, 2023 (incorporated by reference to Exhibit (p)(ii) to Post-Effective Amendment No. 22 to Registrant’s Registration Statement on Form N-1A, filed on January 10, 2024).
(q)	Powers of Attorney (incorporated by reference to Exhibit (q) to Post-Effective Amendment No. 6 to Registrant’s Registration Statement on Form N-1A filed on November 4, 2022).

Item 29. CONTROL PERSONS.

No person is directly or indirectly controlled by or under common control with Calamos Alternative Nasdaq & Bond ETF.

Item 30. INDEMNIFICATION.

Article IX of the Second Amended and Restated Trust Instrument of the Registrant (the “Trust Instrument”) (Exhibit (a)(ii) to this registration statement) provides that, subject to certain exceptions and limitations, every person who is, or has been, a trustee or an officer or employee of the Trust or is or was serving at the request of the Trust as a trustee, director, officer, employee or agent of another organization in which the Trust has any interest as a shareholder, creditor or otherwise (“Covered Person”) shall be indemnified by the Trust and each series to the fullest extent permitted by law against liability and against all expenses reasonably incurred or paid by him or her in connection with any claim, action, suit or proceeding in which he or she becomes involved as a party or otherwise by virtue of his or her being or having been a Covered Person and against amounts paid or incurred by him or her in the settlement thereof. To the extent required under the 1940 Act, but only to such extent, no indemnification shall be provided hereunder to a Covered Person: (i) who shall have been adjudicated by a court or body before which the proceeding was brought to be liable to the Trust or its shareholders by reason of willful misfeasance, bad faith, gross negligence or reckless disregard of the duties involved in the conduct of his or her office; or (ii) in the event of a settlement, unless there has been a determination that such Covered Person did not engage in willful misfeasance, bad faith, gross negligence or reckless disregard of the duties involved in the conduct of his or her office: (A) by the court or other body approving the settlement; (B) by at least a majority of those trustees who are neither interested persons of the Trust nor are parties to the matter based upon a review of readily available facts (as opposed to a full trial-type inquiry); or (C) by written opinion of independent legal counsel based upon a review of readily available facts (as opposed to a full trial-type inquiry).

The Trust Instrument also provides that if any shareholder or former shareholder of any series is held personally liable solely by reason of his or her being or having been a shareholder and not because of his or her acts or omissions or for some other reason, the shareholder or former shareholder (or his or her heirs, executors, administrators or other legal representatives or, in the case of any entity, its general successor) shall be entitled out of the assets belonging to the applicable series to be held harmless from and indemnified against all loss and expense arising from such liability. The Trust, on behalf of the affected series, shall, upon request by such shareholder or former shareholder, assume the defense of any claim made against him or her for any act or obligation of the series and satisfy any judgment thereon from the assets belonging to the series. Neither the Trust nor the applicable series shall be responsible for satisfying any obligation arising from such a claim that has been settled by the shareholder without the prior written notice to, and consent of, the Trust. Except as otherwise specifically provided in this Trust Instrument or in the Bylaws, the Trust shall have no obligation to indemnify or hold harmless any shareholder against any loss or expense arising under any circumstances whether in connection with a proceeding of any kind or otherwise.

The Registrant, its trustees and officers, its investment adviser, the other investment companies advised by the adviser and certain persons affiliated with them are insured, within the limits and subject to the limitations of the insurance, against certain expenses in connection with the defense of actions, suits or proceedings, and certain liabilities that might be imposed as a result of such actions, suits or proceedings. The insurance expressly excludes coverage for any trustee or officer whose personal dishonesty, fraudulent breach of trust, lack of good faith, or intention to deceive or defraud has been finally adjudicated or may be established or who willfully fails to act prudently.

Insofar as indemnification for liabilities arising under the Securities Act of 1933 (the “Securities Act”) may be permitted to trustees, officers, and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a trustee, officer, or controlling person of the Registrant in the successful defense of any action, suit, or proceeding) is asserted by such trustee, officer, or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

Item 31. BUSINESS AND OTHER CONNECTIONS OF INVESTMENT ADVISER.

The information in the Statement of Additional Information under the captions “Management” and “Investment Advisory Services” is incorporated by reference.

Item 32. PRINCIPAL UNDERWRITER.

(a) Calamos Financial Services LLC (“CFS”) serves as principal underwriter for the following investment companies registered under the Investment Company Act of 1940, as amended: Calamos Investment Trust, Calamos Advisors Trust, Calamos Antetokounmpo Sustainable Equities Trust, and Calamos ETF Trust.

(b) Information on the officers of CFS is set forth below. CFS has no directors. The principal business address for all named individuals, except Mr. Ojala, is 2020 Calamos Court, Naperville, Illinois 60563. Mr. Ojala’s principal business address is 215 North Peoria Street, Chicago, Illinois 60607.

Name	Position with Underwriter	Position with Registrant
John S. Koudounis	President and Chief Executive Officer	Vice President
Robert F. Behan	Principal Executive Officer and Chief Distribution Officer	Vice President
Daniel Dufresne	Executive Vice President, Chief Operating Officer	Vice President
Christian A. Helmetag	Principal Financial Officer and Principal Operations Officer	None
Erik D. Ojala	General Counsel and Secretary	Vice President and Secretary
Jacqueline E. Sinker	Chief Compliance Officer	None

(c) There are no commissions or other compensation received from the Registrant directly or indirectly, by any principal underwriter who is not an affiliated person of the Registrant or an affiliated person of an affiliated person.

Item 33. LOCATION OF ACCOUNTS AND RECORDS.

All such accounts, books, and other documents are maintained at the offices of the Registrant, at the offices of the Registrant’s investment adviser, Calamos Advisors LLC, and CFS, the Registrant’s principal underwriter, 2020 Calamos Court, Naperville, Illinois 60563, or at the offices of the custodian and transfer agent, State Street Bank and Trust Company, One Congress Street, Suite 1, Boston, Massachusetts, 02114.

Item 34. MANAGEMENT SERVICES.

None.

Item 35. UNDERTAKINGS.

None.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this Registration Statement under Rule 485(b) under the Securities Act of 1933 and it has duly caused this registration statement to be signed on its behalf by the undersigned, duly authorized, in the City of Naperville, and the State of Illinois on the 7^th day of February, 2024.

Calamos ETF Trust
By:	/s/ John P. Calamos, Sr.
	John P. Calamos, Sr.
	Trustee and President

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed below by the following persons in the capacities and on the dates indicated.

Name	Title	Date
/s/ John P. Calamos, Sr.	Trustee and President (principal executive officer)	February 7, 2024
John P. Calamos, Sr.
/s/ John E. Neal*	Trustee	February 7, 2024
John E. Neal
/s/ William Rybak*	Trustee	February 7, 2024
William Rybak
/s/ Virginia G. Breen*	Trustee	February 7, 2024
Virginia G. Breen
/s/ Lloyd A. Wennlund*	Trustee	February 7, 2024
Lloyd A. Wennlund
/s/ Karen L. Stuckey*	Trustee	February 7, 2024
Karen L. Stuckey
/s/ Christopher M. Toub*	Trustee	February 7, 2024
Christopher M. Toub
/s/ Thomas E. Herman	Vice President and Chief Financial Officer (principal accounting officer)	February 7, 2024
Thomas E. Herman

* An original power of attorney authorizing John P. Calamos, Sr. to execute this Registration Statement, and amendments thereto, for each of the trustees of the Registrant on whose behalf this Registration Statement is filed, was previously executed, and previously filed as an exhibit.

By:	/s/ John P. Calamos, Sr.
	John P. Calamos, Sr.
	Attorney-in-Fact
	February 7, 2024