BACKGROUND: Lung cancer is the leading cause of cancer death. Surgery remains the main method of managing early-stage disease. Minimal-access video-assisted thoracoscopic surgery results in less tissue trauma than open surgery; however, it is not known if it improves patient outcomes. OBJECTIVE: To compare the clinical effectiveness and cost-effectiveness of video-assisted thoracoscopic surgery lobectomy with open surgery for the treatment of lung cancer. DESIGN, SETTING AND PARTICIPANTS: A multicentre, superiority, parallel-group, randomised controlled trial with blinding of participants (until hospital discharge) and outcome assessors conducted in nine NHS hospitals. Adults referred for lung resection for known or suspected lung cancer, with disease suitable for both surgeries, were eligible. Participants were followed up for 1 year. INTERVENTIONS: Participants were randomised 1 : 1 to video-assisted thoracoscopic surgery lobectomy or open surgery. Video-assisted thoracoscopic surgery used one to four keyhole incisions without rib spreading. Open surgery used a single incision with rib spreading, with or without rib resection. MAIN OUTCOME MEASURES: The primary outcome was self-reported physical function (using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30) at 5 weeks. Secondary outcomes included upstaging to pathologic node stage 2 disease, time from surgery to hospital discharge, pain in the first 2 days, prolonged pain requiring analgesia at > 5 weeks, adverse health events, uptake of adjuvant treatment, overall and disease-free survival, quality of life (Quality of Life Questionnaire Core 30, Quality of Life Questionnaire Lung Cancer 13 and EQ-5D) at 2 and 5 weeks and 3, 6 and 12 months, and cost-effectiveness. RESULTS: A total of 503 patients were randomised between July 2015 and February 2019 (video-assisted thoracoscopic surgery, n = 247; open surgery, n = 256). One participant withdrew before surgery. The mean age of patients was 69 years; 249 (49.5%) patients were men and 242 (48.1%) did not have a confirmed diagnosis. Lobectomy was performed in 453 of 502 (90.2%) participants and complete resection was achieved in 429 of 439 (97.7%) participants. Quality of Life Questionnaire Core 30 physical function was better in the video-assisted thoracoscopic surgery group than in the open-surgery group at 5 weeks (video-assisted thoracoscopic surgery, n = 247; open surgery, n = 255; mean difference 4.65, 95% confidence interval 1.69 to 7.61; p = 0.0089). Upstaging from clinical node stage 0 to pathologic node stage 1 and from clinical node stage 0 or 1 to pathologic node stage 2 was similar (p ≥ 0.50). Pain scores were similar on day 1, but lower in the video-assisted thoracoscopic surgery group on day 2 (mean difference -0.54, 95% confidence interval -0.99 to -0.09; p = 0.018). Analgesic consumption was 10% lower (95% CI -20% to 1%) and the median hospital stay was less (4 vs. 5 days, hazard ratio 1.34, 95% confidence interval 1.09, 1.65; p = 0.006) in the video-assisted thoracoscopic surgery group than in the open-surgery group. Prolonged pain was also less (relative risk 0.82, 95% confidence interval 0.72 to 0.94; p = 0.003). Time to uptake of adjuvant treatment, overall survival and progression-free survival were similar (p ≥ 0.28). Fewer participants in the video-assisted thoracoscopic surgery group than in the open-surgery group experienced complications before and after discharge from hospital (relative risk 0.74, 95% confidence interval 0.66 to 0.84; p