Exhibit 5.1

Yigal Arnon (1929-2014) Dror Vigdor Amalia Meshi Amnon Lorch Hagai Shmueli Barry Levenfeld David H. Schapiro Hagit Bavly Orna Sasson Barak Tal Shiri Shaham Doron Tamir Daniel Abarbanel Niv Zecler Ofer Argov Gidon Weinstock David Osborne Gil Oren Ronit Amir Orly Tsioni Mordehai Baicz Barak Platt Benjamin Horef Yoran Gill Asaf Eylon Daniel Marcovici Adrian Daniels Yuval Shalheveth Jacob Ben Chitrit Peter Sugarman Ben Sandler Boaz Fiel Joeri Kreisberg Simon Weintraub Ruth Loven Yarom Romem Adam Spruch Yuval Bargil Eliran Furman Eran Lempert Ofir Levy
Daniel Green Hanital Belinson Yoheved Novogroder
Oren Roth
Dror Varsano Odelia Sidi Shira Lahat Micki Shapira Eran Zach Ido Chitman Aner Hefetz David Akrish Nir Rosner Assaf Mesica Liron Hacohen Guy Fuhrer Ezra Gross David Roness Eli Greenbaum Lee Maor
Nimrod Vromen Guy Sagiv Micha Tollman Shani Rapoport Lior Gelbard Keren Tal Naftali Nir Yael Hoefler Sagi Schiff Netanella Treistman Daniel Damboritz Yulia Lazbin Joshua Lieberman Eyal Aichel Michal Sagmon Hila Rot
Neta Goshen Roy Masuri Chen Lanir Daphna Livneh Tamar Gilboa
Adi Samuel Shlomi Schneider Alona Toledano
Elad Offek Yuval Shamir Dana Heller
Liat Pillersdorf Avi Anouchi Shay Fahima
Sivan Gilron Dotan Tomer Bar-Nathan
Evan Schendler
Lihi Katzenelson
Inbar Hakimian-Nahari Shahar Uziely Edan Regev
Yehudit Biton Gitit Ramot-Adler
Omri Schnaider Shiran Sofer Rinat Michael
Adi Attar Daniella Milner
Amos Oseasohn Guy Kortany Goor Koren
Adi Daniel
Miriam Friedmann Roni Osborne Ortal Zanzuri Reut Sasson
Roey Sasson Shir Eshkol Moshe Medved Lior Sofer Nir Rodnizky Noa Slavin
Michael Horowitz Guy Fatal
Shani Lorch Ira Evental Itamar Cohen
Shai Margalit Ofir Schwartz
Meital Singer
Yonatan Whitefield Moshe Lankry
Nir Kamhi Shira Teger Itamar Glazer Rachel Lerman Ravid Saar Debbie Shalit Sophie Blackston Eti Elbaz Igor Baraz
Elad Morgenstern
Ron Ashkenazi Dafna Raz Sara Haber
Carmel Nudler Yael Nassi Ilan Akouka Yehonatan Cohen David Shmulevitz Tair Cherbakovsky Amit Zomer Fedida Ophir Dagan
Yael Meretyk Hanan Nataly Damary
Shiran Glitman Michael Rosenblit
Dani Weissberg Lareine Khoury Nohar Hadar Shirley Youseri Nitzan Kahana Tali Har-Oz
Niv Blacher Noa Bombigher
Tal Alon Liad Kalderon Natalie Korenfeld Moshe Pasker Mazi Ohayon Nitzan Fisher-Conforti Victoria Savu Derora Tropp Amos Shiffman Hila Amiel
Chaim Cohen Shine Shaham Maytal Spivak Avraham Schoen Or Lev Or Karabaki Elan Loshinsky Eyal Sharf Ron Shaham Yarden Hadar Ariel Even Noah Zivan Daniel Gazit
Josh Hauser Ron Jacoby
Eitan Cohen Itai Guttel Dor Brown Artium Gorelik Maor Alev Tamar Drori Vered Glaubach Yair Taitelbaum Gilad Lindenfeld Gabi Priel Regina Pevzner Sophy Litvin   Roy Keidar Of Counsel   Paul H. Baris (1934-2010) Rami Kook Nira Kuritzky Eran Ilan

Tel Aviv | June 28, 2019

Enlivex Therapeutics Ltd.

14 Einstein Street

Nes Ziona, Israel 7403618

Re: Enlivex Therapeutics Ltd. Shelf Registration Statement on Form F-3

Ladies and Gentlemen:

We have acted as special Israeli counsel for Enlivex Therapeutics Ltd., a company organized under the Laws of the State of Israel (the “Company”), in connection with certain Israeli law matters involved in the preparation of a Shelf Registration Statement on Form F-3 (the “Registration Statement”), being filed by the Company with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), relating to the registration of 682,631 ordinary shares, NIS 0.40 per share, of the Company (“Ordinary Shares”), of the Company to be offered and sold by certain shareholders of the Company (the “Securities”).

In connection with our representation of the Company, and as a basis for the opinions hereinafter set forth, we have examined originals, or copies certified or otherwise identified to our satisfaction, of the following:

(1) the Registration Statement;

(2) the Company’s Articles of Association, as amended to the date hereof (the “Charter”); and

(3) such other documents and records and other certificates and instruments and matters of law as we have deemed necessary or appropriate to express the opinions set forth below, in each case subject to the assumptions, limitations and qualifications stated herein.

1 Azrieli Center, Tel Aviv, 6702101 | Phone: +972-3-6087777 | Fax: +972-3-6087724

31 Hillel Street, Jerusalem, 9458131 | Phone: +972-2-6239239 | Fax: +972-2-6239233

www.arnon.co.il | info@arnon.co.il

In rendering the opinions set forth below, we have assumed the genuineness of all signatures, the legal capacity of natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as duplicates or certified or conformed copies and the authenticity of the originals of such latter documents.

As to matters of fact material to this opinion, we have relied to the extent we deemed reasonably appropriate upon representations or certificates of officers or directors of the Company, without independently verifying the accuracy of such documents, records and instruments.

We have further assumed that: (i) the Registration Statement and any amendments thereto will be effective under the Securities Act, that no stop orders will have been issued by the Commission with respect to the Registration Statement and that the Registration Statement will comply with all applicable laws at the time the Securities are offered or issued as contemplated by the Registration Statement; (ii)  all Securities will be issued and sold in compliance with the applicable provisions of the Securities Act and the securities or blue sky laws of various states and in the manner stated in the Registration Statement, any amendment thereto, the prospectus contained therein and supplements to the prospectus and pursuant to Rule 415 under the Securities Act; and (iii) any purchase, underwriting or similar agreement relating to Securities being offered will have been duly authorized, executed and delivered by the Company and the other parties thereto.

Based upon and subject to the foregoing, and subject to the assumptions, limitations and qualifications stated herein, we are of the opinion that, the Securities to be registered under the Registration Statement have been duly authorized, validly issued and fully paid, and are nonassessable.

This opinion letter is limited to the matters stated herein, and no opinions may be implied or inferred beyond the matters expressly stated herein. We assume no obligation to supplement this opinion if any applicable law changes after the date hereof or if we become aware of any fact that might change the opinion expressed herein after the date hereof.

We do not express any opinion herein concerning any law other than the laws of the State of Israel.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and to the use of the name of our firm therein. In giving this consent, we do not admit that we are within the category of persons whose consent is required by Section 7 of the Securities Act.

Sincerely,

/s/ Yigal Arnon & Co.

Yigal Arnon & Co.

1 Azrieli Center, Tel Aviv, 6702101 | Phone: +972-3-6087777 | Fax: +972-3-6087724

31 Hillel Street, Jerusalem, 9458131 | Phone: +972-2-6239239 | Fax: +972-2-6239233

www.arnon.co.il | info@arnon.co.il

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