We study howgovernment policies and corporate commitments to decarbonize interact under two externalities: environmental damages and green innovation spillovers. Unconstrained carbon taxes and innovation subsidies could achieve rst-best outcomes, but when government policies face constraints, commitments by large rms and institutional investors can serve as prot-driven coordination devices that spur green innovation and technology adoption, and thereby reduce overall transition costs. Firm commitments also enhance government policy credibility by lowering the need for high future carbon taxes. Our empirical evidence confirms that firm size and green common ownership drive Net Zero commitments and decarbonization investments.