Intellectual property (IP) rights are a major component of firms’ strategies to appropriate the benefits of their innovations. This paper aims at assessing the interactions between two types of IP rights, namely patents and trademarks. We first model the effect of these two types of IP rights on the returns of innovations for firms. Based on a supermodularity analysis, we then show that the complementarity between trademarks and patents varies according to the characteristics of the market. Depending on the levels of advertising’s spillovers and depreciation rate, trademarks are found to be complementary or not to patents. Finally, based on a data set encompassing the IP activity of a sample of publicly traded firms among the top corporate R&D investors worldwide, we find that patents and trademarks are complementary in chemical and pharmaceutical sectors, but not in Information and Communication Technologies (ICT) sectors.