Non-small-cell lung cancer (NSCLC) is a widespread and particularly aggressive form of cancer. Patients with NSCLC and early metastases typically have poor prognosis, highlighting the critical need for additional drugs to improve disease outcome following surgical resection. The present study aimed to determine if Siamese crocodile bile (SCB) had an anti‑cancer effect on NCI‑H1299 human NSCLC cells. The inhibitory mechanism of SCB was examined in cell culture and nude mice. In vitro experimental results revealed that SCB inhibited the proliferation and colony‑forming ability of NCI‑H1299 cells by arresting cell cycle and inducing apoptosis. The loss of the mitochondrial membrane potential and the release of cytochrome c indicated that SCB treatment may lead to mitochondrial dysfunction in NCI‑H1299 cells. At the molecular level, SCB altered the ratio of protein expression of Bax/Bcl‑2 and activated associated caspases, suggesting that intrinsic pathway involvement in the SCB‑induced apoptosis of NCI‑H1299 cells. In the in vivo experiments, intraperitoneal injection of SCB for 4 weeks inhibited xenograft tumor growth by 46.8% without observable toxicity in nude mice. Immunohistochemistry analysis of proliferating cell nuclear antigen and vascular endothelial growth factor also revealed that SCB inhibited cell proliferation and metastasis in NSCLC xenograft tumors. Overall, SCB exerted an anti-cancer effect on NCI‑H1299 human NSCLC cells in vitro and in vivo and may have therapeutic potential for the treatment of human NSCLC.