This article provides a new account of psychiatric researchers’ investigation of race and mental disorder in the nineteenth and early twentieth centuries. I argue that Kraepelin’s project of comparative psychiatry is more continuous with earlier research on race and mental disorder and colonial psychiatry than is commonly thought. Specifically, I argue that Kraepelin’s project had the following key conceptual foundations: the clinical research agenda of his earlier work in Heidelberg and Munich, as has previously been argued by Engstrom and Crozier (2018); the racial and colonial psychiatry of his predecessors; and Wundt’s Völkerpsychologie. I also offer a reflection on the concept of race. Researchers understood race in biological, social, cultural, and psychological terms and struggled to isolate race as a causal variable from others, such as culture and nationality. I also argue that it was precisely because of this heterogenous concept of race that the colonial and racial psychiatry of his predecessors influenced Kraepelin’s project of comparative psychiatry, which investigated the impact on psychopathology of cultural and psychological differences. This thesis about the development of comparative psychiatry makes a novel contribution to our understanding of colonial psychiatry.