Saikosaponin‑d (SSd), a triterpene saponin compound derived from Bupleurum radix, has been shown to have a cytotoxic effect on various cancer cell lines. However, its effect on prostate cancer cells has remained unexplored. The present study reports the apoptosis‑inducing effect of SSd on the DU145 human prostate carcinoma cell line. Treatment with SSd inhibited DU145 cell proliferation in a concentration‑dependent manner. Flow cytometric analysis showed that SSd inhibited the proliferation of DU145 cells by induction of apoptosis and cell cycle arrest at G0/G1 phase. Further mechanistic experiments demonstrated that SSd arrested the cell cycle at G0/G1 phase via upregulation of p53 and p21 and induced apoptosis by modulating B‑cell lymphoma 2 family proteins, dissipation of the mitochondrial membrane potential, release of cytochrome c into the cytosol and activation of caspase‑3. In conclusion the present study indicated that SSd induced apoptosis in DU145 cells by the intrinsic apoptotic pathway. Therefore, SSd may become a leading candidate drug for the therapy of prostate carcinoma.