We examine the effects of China's 2009–2010 stimulus package for innovation differentials between state-owned firms (SOEs) and privately-owned firms (POEs). Using a unique dataset of Chinese manufacturing firms, we find that in the pre-stimulus period SOEs patent at a lower rate than POEs in the least inventive patent category, and at a comparable rate in the more inventive categories. Post-stimulus, SOEs patent at an even lower rate relative to POEs in the least inventive category, but significant, positive SOE-POE patent rate differentials emerge in more inventive patent categories. The stimulus disproportionately benefited SOEs with higher investment subsidies and lower finance costs—institutional support which we find mediates roughly 45 percent of all positive effects of state-ownership for innovation. Institutional support produces larger SOE-POE innovation differentials among firms in strategic sectors and located in high-marketization provinces, and for centrally controlled SOEs.