Social enterprises (SEs) strive to balance social missions with financial sustainability. They are a very heterogenous group. While some SEs are highly innovative, others are not. A key challenge is identifying and assessing their level of innovation, as traditional metrics like R&D spending and patents, which focus on technological and science-based innovation, often fall short. This is because SEs frequently innovate in areas such as organizational processes, business models, and services. Against this background, we explore the potential of trademarks as a new way of identifying innovative SEs within the group of SEs. Using a large sample of SEs from Germany, we examine the relationship between trademarks and the innovativeness of SEs through text-based analyses of SE websites and a survey. Additionally, we investigate the underlying reasons SEs choose to register (or not register) trademarks, recognizing that trademarks can serve various purposes. Our findings reveal that innovative SEs are more likely to file trademarks, primarily to protect their innovations and associated brands, pursuing market orientation, and scaling their social impact. These insights deepen our understanding of the heterogeneity among SEs and contribute to the growing conversation on the role of intellectual property rights in creating positive effects for society.