Form S-1 Better Therapeutics,

Exhibit 5.1

November 26, 2021

Better Therapeutics, Inc.

548 Market St #49404

San Francisco, CA 94104

Re: Securities Registered under Registration Statement on Form S-1

Ladies and Gentlemen:

We have acted as counsel to you in connection with your filing of a Registration Statement on Form S-1 (as amended or supplemented, the “Registration Statement”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), relating to the registration by Better Therapeutics, Inc., a Delaware corporation (the “Company”) of up to 20,406,908 shares (the “Selling Stockholder Shares”) of the Company’s common stock, $0.0001 par value per share, to be sold by the selling stockholders listed in the Registration Statement under “Selling Stockholders” (the “Selling Stockholders”).

We have reviewed such documents and made such examination of law as we have deemed appropriate to give the opinions set forth below. We have relied, without independent verification, on certificates of public officials and, as to matters of fact material to the opinions set forth below, on certificates of officers of the Company.

The opinion set forth below is limited to the Delaware General Corporation Law.

Based on the foregoing, we are of the opinion that the Selling Stockholder Shares have been duly authorized and validly issued and are fully paid and non-assessable.

We hereby consent to the inclusion of this opinion as Exhibit 5.1 to the Registration Statement and to the references to our firm under the caption “Legal Matters” in the Registration Statement. In giving our consent, we do not admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations thereunder.

Exhibit 23.1

Independent Registered Public Accounting Firm’s Consent

We consent to the inclusion in this Registration Statement of Better Therapeutics, Inc. (f/k/a Mountain Crest Acquisition Corp. II) on Form S-1 of our report dated March 30, 2021, with respect to our audit of the financial statements of Mountain Crest Acquisition Corp. II (now known as Better Therapeutics, Inc.) as of December 31, 2020 and for the period from July 31, 2020 (inception) through December 31, 2020, which report appears in the Prospectus, which is part of this Registration Statement. We were dismissed as auditors on November 22, 2021 and, accordingly, we have not performed any review or audit procedures with respect to any financial statements appearing in the prospectus for the periods after the date or our dismissal. We also consent to the reference to our Firm under the heading “Experts” in such Prospectus.

Exhibit 23.2

Consent of Independent Registered Public Accounting Firm

We consent to the use in this Registration Statement on Form S-1 of Better Therapeutics, Inc. (formerly Mountain Crest Acquisition Corp. II) of our report dated March 19, 2021, relating to the financial statements of Better Therapeutics OpCo, Inc. (formerly Better Therapeutics, Inc.), as of and for the years ended December 31, 2019 and December 31, 2020 appearing elsewhere in this Registration Statement.

We also consent to the reference of our firm under the heading “Experts” in such Registration Statement.