Cyclin-dependent kinase inhibitor 3 (CDKN3) belongs to the dual-specificity protein phosphatase family, which is hypothesized to regulate cell cycle progression in tumor cells. However, whether CDKN3 is a potential therapeutic target for breast cancer remains to be elucidated. The present in vitro study aimed to investigate the potential roles of CDKN3 in breast cancer. Breast cancer cell lines were used to detect CDKN3 expression, and CDKN3 expression was silenced to investigate its role in cell apoptosis, cell cycle arrest and migration. The underlying mechanisms were screened by detecting proliferating cell nuclear antigen (PCNA), Ras homolog gene family, member A (RhoA), vimentin, B‑cell lymphoma 2 (Bcl‑2) and Bcl‑2‑associated X protein (Bax) expression. CDKN3 was highly expressed in MCF‑7 and BT474 cell lines. The silencing of CDKN3 in MCF‑7 and BT474 cell lines promoted cell apoptosis, induced G1 phase cell cycle arrest and inhibited cell migration. The expression levels of PCNA, RhoA, vimentin and Bcl‑2 were downregulated following CDKN3 silencing. Conversely, Bax expression was increased, as compared with the vehicle control. These results suggest that CDKN3 acts as an oncogene during breast cancer progression. The in vitro silencing of CDKN3 promoted apoptosis, induced G1 phase cell cycle arrest and inhibited cell migration. Possible mechanisms are associated with the regulation of PCNA, Bcl‑2, vimentin, RhoA and Bax expression. CDKN3 may therefore be considered a potential target for the treatment of breast cancer.