Exhibit 5.1

Weil, Gotshal & Manges LLP

767 Fifth Avenue

New York, New York 10153

(212) 310-8000

December 29, 2009

CareFusion Corporation

3750 Torrey View Court

San Diego, California 92130

Ladies and Gentlemen:

We have acted as counsel to CareFusion Corporation, a Delaware corporation (the “Company”), in connection with the preparation and filing with the Securities and Exchange Commission of the Company’s Registration Statement on Form S-1 (the “Registration Statement”), under the Securities Act of 1933, as amended, relating to the registration of 35,882,301 shares of common stock, par value $0.01 per share (the “Common Stock”). The Common Stock is to be offered and sold by Cardinal Health, Inc., the selling stockholder.

In so acting, we have examined originals or copies (certified or otherwise identified to our satisfaction) of (i) the Amended and Restated Certificate of Incorporation of the Company; (ii) the Amended and Restated Bylaws of the Company, (iii) the Registration Statement; (iv) the prospectus, which forms a part of the Registration Statement; and (vi) such corporate records, agreements, documents and other instruments, and such certificates or comparable documents of public officials and of officers and representatives of the Company, and have made such inquiries of such officers and representatives, as we have deemed relevant and necessary as a basis for the opinion hereinafter set forth.

In such examination, we have assumed the genuineness of all signatures, the legal capacity of all natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as certified, conformed or photostatic copies and the authenticity of the originals of such latter documents. As to all questions of fact material to this opinion that have not been independently established, we have relied upon certificates or comparable documents of officers and representatives of the Company.

Based on the foregoing, and subject to the qualifications stated herein, we are of the opinion that the Common Stock, when sold as contemplated in the Registration Statement, will be duly authorized, validly issued, fully paid and non-assessable.

We hereby consent to the filing of this letter as an exhibit to the Registration Statement and to the reference to our firm under the caption “Legal Matters” in the prospectus which is a part of the Registration Statement.

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