Recently, Pt-based bimetallic nanoparticles have drawn much attention because of their great catalytic performance and wide applications in diverse fields. In this work, we report that bimetallic Pt–In nanoparticles with uniform size distribution and controllable composition can be synthesized through a one-step, facile colloidal approach. Various characterization tools such as XRD, TEM, XPS, and synchrotron techniques have been used to characterize the as-obtained nanoparticles. It is demonstrated that the Pt and In elements are homogeneously distributed in the whole nanoparticle. The bimetallic Pt–In nanoparticles have shown great catalytic performance, including high activity, high selectivity, and high stability, for the propane dehydrogenation reaction to produce propene, one of the most important chemicals. The excellent catalytic performance makes Pt–In bimetallic nanoparticles promising catalysts in future industrial application.