Purpose We investigated the efficiency of the Simplified Comorbidity Score (SCS) for predicting postoperative complications and prognosis in elderly patients undergoing video-assisted thoracoscopic surgery (VATS) for lung cancer. Methods We reviewed 216 patients aged 75 years or older, who underwent pulmonary resection by VATS for lung cancer between January, 2005 and December, 2012. The SCS assigns different scores to patients' comorbidities; namely, smoking (n = 7); diabetes mellitus (n = 5); renal insufficiency (n = 4); and respiratory, neoplastic, and cardiovascular comorbidities or alcoholism (n = 1 each). Patients were divided into a high SCS group (SCS = 9; n = 154) and a low SCS group (< 9; n = 62), for a comparative analysis of differences in perioperative factors and prognoses. Results Limited resection was more frequent in the high SCS group (58 %) than in the low SCS group (40 %; P = 0.02). Postoperative complications were more frequent in the high SCS group (45 %) than in the low SCS group (15 %; P < 0.01). A logistic regression analysis revealed that a high SCS was significantly predictive of postoperative complications (odds ratio 2.7; P = 0.02). The 5-year overall survival rate was 79 % for the low SCS group and 52 % for the high SCS group (P < 0.01). Conclusions The SCS can predict the likelihood of postoperative complications and prognosis of elderly patients with VATS-treated lung cancers.