MicroRNAs (miRNAs) are strongly implicated in various cancers, including prostate cancer. Recently, microRNA-455-3p (miR-455-3p) has been shown to be aberrantly expressed in many tumor tissues, but its functions in tumorigenesis remain unknown. In this study, we investigated the role of miR-455-3p in prostate cancer. We found that miR455-3p is markedly downregulated in prostate cancer cell lines and clinical tumor specimens. Gain -of -function and loss -of function studies showed that miR-455-3p promotes prostate cancer cell growth both in vitro and in vivo. Bioinformatics analysis and Luciferase reporter assays demonstrated that miR455-3p directly targets and suppresses eIF4E, the rate -limiting factor for cap -dependent translation, which plays important roles in the initiation and progression of prostate cancers. Further studies demonstrated that miR-455-3p inhibits cap dependent translation and the proliferation of prostate cancer cells through targeting eIF4E. Taken together, our findings suggest that miR-455-3p functions as a tumor suppressor by directly targeting eIF4E in prostate carcinogenesis and may be used as a potential target for therapeutic intervention in prostate cancer.