Technology to visualize small prostate cancers is urgently needed because of the difficulty of discriminating prostate cancer from normal tissue with the naked eye, and a fluorescence imaging method would be advantageous. Here, we describe the design and synthesis of a fluorogenic probe (Ac-KQLR-HMRG) that is activated by hepsin and matriptase (proteases over-expressed in prostate cancer). Ac-KQLR-HMRG exhibited significant turn-on fluorogenicity in the presence of hepsin (180-fold) and matriptase (80-fold) and allowed specific fluorescence imaging of various prostate cancer cell line in vitro. In addition, the probe enabled rapid imaging (within 1-10 min) of small prostate cancer nodules in mouse models of disseminated peritoneal tumor and orthotopic tumor.