We aimed to assess the effects of gametogenetin‐binding protein 2 (GGNBP2) on the proliferation, invasion and migration of prostate cancer PC‐3 cells. PcDNA3‐HisC‐GGNBP2 was transfected to overexpress GGNBP2. Proliferation was tested by MTT assay, and migration and invasion were detected by Transwell assay. Cell cycle was detected by flow cytometry. The protein expressions of COX‐2, cyclin D1, PI3K, Akt and p‐Akt were detected by Western blot. A subcutaneous xenograft model of prostate cancer was established. Mice were randomly divided into three groups (n = 9) and intratumorally injected with pcDNA3‐HisC‐GGNBP2, pcDNA3‐HisC and normal saline respectively. The xenograft tumour volume was measured every 3 days, and weight was measured after 2 weeks. After GGNBP2 overexpression, the proliferation, migration and invasion capacities of PC‐3 cells decreased, and cell cycle was arrested in the G1 phase. The protein expressions of COX‐2, cyclin D1, PI3K, Akt and p‐Akt all reduced. The tumour volume and weight of pcDNA3‐HisC‐GGNBP2 group were significantly lower than those of pcDNA3‐HisC group (p < .05). The proliferation capacity of GGNBP2‐overexpressing prostate cancer cells is significantly attenuated, tumour growth is significantly inhibited, and cell cycle is arrested in the G1 phase. GGNBP2 overexpression affects the growth of castration‐resistant prostate cancer via the PI3K/Akt signalling pathway.