Recently, traditional Chinese medicine has gained attention for its potential use as a chemotherapeutic agent. Pseudolaric acid B (PAB) is a diterpene acid isolated from Pseudolarix kaempferi and possesses antifungal, antimicrobial, antifertility and antiangiogenic properties. It was also reported that PAB may inhibit proliferation and induce apoptosis in various types of cancer. However, its effects on A549 lung cancer cells remain to be determined. The present study aimed to determine the potential roles of PAB in the proliferation and apoptosis of A549 cells. The results showed that PAB inhibited A549 cell proliferation in a time‑ and dose‑dependent manner. Fluorescence microscopy results showed that cells treated with 20 µmol/l PAB for 24 h exhibited karyorrhexis and apoptotic body formation. In addition, A549 cells were treated with 5, 10, 20, 40 or 80 µmol/l PAB for 24 h and apoptosis was analyzed using Annexin‑V/propidium iodide kit. The apoptosis rates were 8.95, 18.71, 24.66, 35.02 and 43.64%, respectively, in PAB‑treated cells and 0.80% in the control group. Furthermore, western blot analysis showed that PAB treatment upregulated the protein levels of Bax, Bad and downregulated Bcl‑2 and Bcl‑xl expression. In conclusion, PAB may serve as a potent chemotherapeutic agent against human lung cancer.