This paper investigates the effects of going public on firm innovation by comparing the innovation activities of firms that go public with firms that choose to not undergo an initial public offering (IPO) and remain privately held. Going public here is a transformation of a privately held firm into a public firm, i.e. the first time for the firm to publicly trade in stock markets. The combination of a propensity score matching (PSM) and a difference-in-difference (DiD) methods are adopted to measure the innovation trends in terms of patent applications. Using the patent-based metric, firm innovation increases following IPOs. Comparing to the innovation activities of privately held peers, going public can boost the patent growth rate of firms and delay the downward trend of patent growth in the two years following IPOs.