I analyze whether a change in patent systems differentially affects firm-level innovation investments at patent-valuing firms of different sizes. Using legally required, economically representative, U.S. Census Bureau microdata, I separate firms into groups based on a firm’s response to a question asking it to rank the degree of patent importance to its business and firm-size. I then measure how firms’ innovation inputs/outputs respond to the America Invents Act (AIA). Results show the AIA reduced innovation investments at smaller, patent-valuing firms while increasing innovation investments at larger, patent-valuing firms, highlighting differential firm-size effects of patent policy and policy’s importance to investments.