This study aimed to investigate the effects and mechanisms of X-linked inhibitor of apoptosis protein (XIAP)-associated factor 1 (XAF1) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on the apoptosis of A549 lung adenocarcinoma cell lines. Recombinant lentiviral vector of Ad5/F35-XAF1 and controlled lentiviral vector of Ad5/F35-Null were transfected into A549 cells at same multiplicity of infection (MOI), respectively. Based on whether recombinant human TRAIL (rhTRAIL) was added or not, cells were divided into different groups as follows: XAF1 group, XAF1 + TRAIL group, XAF1-Null group, and XAF1-Null + TRAIL group. Following culturing for 48 h, the mRNA and protein expression levels of related genes were determined by reverse transcription-quantitative polymerase chain reaction and western blotting analyses, respectively. Cell proliferationand cell apoptosis were detected by MTT assay and Annexin V-FITC/PI double staining, respectively. Xenograft mice models were established with A549 lung adenocarcinoma cells and treated with recombinant virus Ad5/F35-XAF1 and controlled virus Ad5/F35-Null for immunohistochemical analysis. Expression levels of XAFl at the mRNA and protein levels were significantly higher in the XAF1 group and XAF1 + TRAIL groups when compared with the levels in the other groups (P<0.05). Cleavage of apoptosis-associated proteins, poly ADP-ribose polymerase and caspase-3, was noted in the XAF1 + TRAIL group, whereas they were not detected in other groups. Apoptosis rates of A549 cells in the XAF1, Null + TRAIL and XAFl + TRAIL groups were significantly higher than those in the NOR and Null groups (P<0.05). Apoptotic rates were highest in the XAF1 + TRAIL group. In conclusion, these findings suggest that combined use of XAF1 and TRAIL may synergistically induce the apoptosis of A549 lung adenocarcinoma cells.