Objective To investigate the inhibitory effect of gambogic acid (GA) on the growth of prostate cancer (PCa) cells representing different clinical characteristics. Methods The androgen-dependent PCa cells LNCaP, androgen-resistant PCa cells 22RV1, and neuroendocrine PCa cells PC3 were treated with GA and enzalutamide (Enz). IC₅₀ values of the treated cells were determined by the CCK8 method . The expression levels of androgen receptor (AR), Ki67, Cleaved caspase-3 and Bcl-2 and the apoptosis of the different PCa cells treated with GA were determined by qRT- PCR, Western blot and flow cytometry. PC3 cells were implanted subcutaneously into male nude mice, and then the tumor- bearing mice were divided into three groups at random: Control group, Enz group and GA group. The changes of tumor volume were measured during drug treatment, and the tumor weight was determined after treatment to evaluate the overall effect of drug treatment. Results Compared with Enz, GA displayed achieved better inhibitory effection for of the growth of LNCaP, 22RV1 and PC3 cells, and a lower dose of GA can could reduce the proliferation and activity of these cells. Under the effect of GA, the expression of Ki67 and AR in PCa cells was significantly decreased (P<0.05). With increasing GA concentration, the number of apoptotic PCa cells gradually increased, and the expression of apoptosis-related protein Cleaved caspase-3 increased (P<0.001) and that of bcl-2 decreased (P< 0.001). In vivo, compared with those in the Control group, tumor volume and weight decreased in the Enz group, albeit not significantly, while tumor volume and weight decreased significantly in the GA group (P<0.01). Conclusions GA can inhibit the growth of PCa cells in vivo and in vitro, as well as the expression of AR and Ki67 in these cells. GA can also promote the apoptosis of tumor cells by regulating the expression of Cleaved caspase-3 and Bcl-2 proteins.