The effects of acrylonitrile (ACN) on human umbilical cord mesenchymal stem cells (hUC‑MSCs) remain unknown. The proliferation, differentiation, clonogenicity and apoptosis effects of ACN and/or N‑acetyl‑L‑cysteine (NAC) on hUC‑MSCs were investigated. The results showed that although ACN at a concentration of 0.1 µg/ml did not affect proliferation or the morphology of hUC‑MSCs compared with the control, osteogenic differentiation and the positive rate of alkaline phosphatase staining in the experimental group were significantly lower compared with the control (P<0.01). All of the effects of ACN were counteracted using NAC, a typical antioxidant. Using a flow cytometry assay, it was observed that ACN induced apoptosis in hUC‑MSCs. The results indicated that the toxic effect produced by ACN on hUC‑MSCs is based on a redox mechanism.