Radiotherapy is currently the major therapeutic strategy for patients with lung cancer. However, radioresistance and various side effects continue to present challenging issues for this form of treatment. A recent study demonstrated that cyclophilin A (CyPA) was overexpressed in non-small cell lung cancer and, therefore, presents a novel potential therapeutic target. In addition, gene-radiotherapy is a novel method for cancer treatment. Therefore, the objective of the present study was to investigate the potential effect of CyPA silencing on radiosensitivity in human lung adenocarcinoma in vitro. The stable CyPA-silencing lung adenocarcinoma (PAa) cell line was generated using lentivirus-mediated small hairpin RNAs. The knockdown of CyPA was determined using fluorescent microscopy and western blot analysis. Cells were irradiated using various doses of cobalt-60 (0, 2, 4, 6 and 8 Gy). The radiosensitizing effects were determined by a clonogenic survival assay. Apoptosis and cell cycle distribution were evaluated using flow cytometry. Silencing of CyPA significantly increased the apoptosis of PAa cells. In addition, the radiosensitivity of cells was markedly enhanced following CyPA silencing. Furthermore, silencing of CyPA, in combination with irradiation, induced G(2)/M phase cell cycle arrest. Taken together, the data suggest that the silencing of CyPA, combined with radiation therapy, may increase the therapeutic efficacy of lung cancer treatment through regulation of the cell cycle and apoptosis-associated signaling pathways.