EX-5.1

Exhibit 5.1

August 26, 2021

Blockchain Coinvestors Acquisition Corp. I

PO Box 1093, Boundary Hall

Cricket Square, Grand Cayman

KY1-1102, Cayman Islands

Re: Registration Statement on Form S-1

Ladies and Gentlemen:

We have acted as special counsel to Blockchain Coinvestors Acquisition Corp. I, a Cayman Islands exempted company (the “Company”), in connection with the initial public offering by the Company of up to 28,750,000 units of the Company (the “Units”) (including up to 3,750,000 Units subject to an over-allotment option), each Unit consisting of one Class A ordinary share of the Company, par value $0.0001 per share (“Class A Ordinary Shares”), and one-third of one redeemable warrant of the Company (each whole warrant, a “Warrant”), each Warrant exercisable for the purchase of one Class A Ordinary Share. The Units, and the Class A Ordinary Shares and Warrants, in each case, included as part of the Units, are collectively referred to herein as the “Securities.” The Securities are included on a registration statement on Form S-1, initially filed by the Company with the Securities and Exchange Commission (the “Commission”) on August 26, 2021 (as amended, the “Registration Statement”, and the related prospectus contained therein, the “Prospectus”), pursuant to the Securities Act of 1933, as amended (the “Securities Act”), and the rules and regulations promulgated thereunder (the “Rules”).

In our capacity as counsel to the Company, we have examined or are otherwise familiar with (a) the form of the Company’s Amended and Restated Memorandum and Articles of Association (the “New Charter”); (b) the Registration Statement; (c) the Prospectus; (d) the form of Underwriting Agreement proposed to be entered into between the Company, Cantor Fitzgerald & Co. and Moelis and Company (the “Underwriting Agreement”); (e) the form of warrant agreement (the “Warrant Agreement”) proposed to be entered into by the Company and Continental Stock Transfer & Trust Company; (f) the form of Unit certificate (together with the Warrant Agreement, the “Transaction Documents”); (g) such of the corporate proceedings with respect to the issuance and sale of the Securities as have occurred prior to or as of the date hereof and (h) such other documents, records and instruments as we have deemed necessary for the purposes of this opinion. In such examination, we have assumed the following without investigation: (i) the authenticity of original documents and the genuineness of all signatures; (ii) the conformity to the originals of all documents submitted to us as copies and (iii) the truth, accuracy and completeness of the information, representations and warranties contained in the records, documents, instruments and certificates we have reviewed. We have also assumed that the Company (1) is duly incorporated and is validly existing and in good standing under the laws of the jurisdiction of its organization; (2) has complied and will comply with all aspects of the laws of the jurisdiction of its organization in connection with the transactions contemplated by, and the performance of its obligations under, the Transaction Documents, including the issuance and sale of the Units and Warrants; (3) has the corporate power and authority to execute, deliver and perform all its obligations under the Transaction Documents, including the issuance and sale of the Units and Warrants and (4) has duly authorized the execution, delivery and performance of all its obligations under the Transaction Documents, including the issuance and sale of the Units and Warrants, by all necessary corporate action of the Company.

Based on the foregoing and subject to the additional exclusions and qualifications set forth below, we are of the opinion that:

When the Registration Statement becomes effective under the Securities Act and the Units are duly issued, delivered and paid for as contemplated in the Registration Statement and in accordance with the terms of the Underwriting Agreement, and assuming the due authorization, execution and delivery thereof by Continental Stock Transfer & Trust Company, as transfer agent, the Units will constitute valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

When the Registration Statement becomes effective under the Securities Act and the Units are duly issued, delivered and paid for as contemplated in the Registration Statement and in accordance with the terms of the Underwriting Agreement, the Warrants included in the Units will constitute valid and binding obligations of the Company, enforceable against the Company.