Background: Cancer pain is a debilitating disorder and a primary determinant of the poor quality of life, and relieving pain is a fundamental strategy in cancer treatment. Most cancer patients have severe pain, also for lung cancer. As such, it is vital to make the best choice of analgesic for lung cancer management. Objectives: The main aim of the present study was to explore the mechanisms and related biological pathways by which nalbuphine influences tumor progression of lung cancer cells. Materials and Methods: First, different concentrations of nalbuphine were used to treat A549 cells, and the concentration at 200 mu M with obvious damage to cell activity of human normal lung epithelial cells (BEAS-2B) was selected for follow-up study. CCK-8, colony formation, wound healing and Transwell assays were performed to examine cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) upon nalbuphine treatment. RT-PCR and western blot were used to assess expression levels of related genes. Results: Nalbuphine inhibited cell vitality of A549 cells, with little effect on human normal lung epithelial cells, BEAS-2B. Nalbuphine suppressed cell proliferation, migration, invasion and EMT in A549 cells Additionally, silence of G protein subunit gamma 2 (GNG2) reversed the nalbuphine-induced inhibition of cancer malignant progression and EMT. Conclusions: Our results demonstrate a new role of nalbuphine in inhibiting the process of malignant progression and EMT in addition to relieving pain, which suggests that nalbuphine may be effective in lung cancer treatment.