The aim of the present study was to investigate the expression levels of transforming growth factor-β (TGF-β) receptor type II (TβRII) and DPC4/Smad4 in the TGF-β signaling pathway and the importance of these expression levels in non-small cell lung cancer (NSCLC). The mRNA and protein expression levels of TβRII and DPC4/Smad4 were detected by reverse transcription-quantitative polymerase chain reaction and western blotting, respectively, in NSCLC and control nonlesional lung tissues of 60 patients. The protein expression levels of DPC4/Smad4 were detected by immunohistochemistry in paraffin-embedded samples of NSCLC. In addition, the correlations among the expression levels of TβRII and DPC4/Smad4 and their association with the clinical and pathological features of NSCLC were analyzed. The expression levels of TβRII and DPC4/Smad4 in NSCLC tissues were significantly lower when compared with the control nonlesional lung tissues (P<0.05). In addition, the expression of TβRII and DPC4/Smad4 in poorly-differentiated NSCLC tissues was significantly lower compared with moderately- or well-differentiated NSCLC tissues (P<0.05). The expression levels of TβRII and DPC4/Smad4 were significantly lower in NSCLC tissues with metastatic lymph nodes compared with tissue without metastatic lymph nodes (P<0.05). Thus, the expression levels were demonstrated to significantly correlate with the clinical and pathological stages, and subsequently were shown to be associated with the occurrence and progression of NSCLC. In conclusion, TβRII and DPC4/Smad4 may play an important role in the tumorigenesis, differentiation and progression of NSCLC via the TGF-β signaling pathway.