Objective <p>In minimally invasive surgeries such as video-assisted thoracic surgery (VATS) and robot-assisted thoracic surgery (RATS), unexpected complications may necessitate conversion to thoracotomy. This study aimed to compare the rates, causes, and implications of conversion to thoracotomy between VATS and RATS.</p> Methods <p>We retrospectively reviewed data from 1135 patients who underwent anatomical lung resection for primary lung cancer via VATS (<i>n</i> = 580) or RATS (<i>n</i> = 555) from 2011 to 2024. Conversion causes were categorized using the Vascular, Anatomy, Lymph node, Technical (VALT) system. Perioperative outcomes and independent predictors of conversion were analyzed via multivariate logistic regression.</p> Results <p>The overall conversion rate was significantly lower in the RATS group than in the VATS group (2.0% vs. 7.8%, <i>p</i> &lt; 0.001). RATS was associated with fewer anatomical (0.9% vs. 3.1%, <i>p</i> = 0.010) and lymph node-related (0.2% vs. 2.6%, <i>p</i> &lt; 0.001), with no significant difference in vascular-related conversions (0.9% vs. 2.1%, <i>p</i> = 0.142). Multivariate analysis identified age ≥ 75&#xa0;year, clinical T2–4, and N1–2 stage as independent risk factors, while RATS use was protective. Emergency conversions were uncommon in both groups, whereas RATS appeared advantageous in technically demanding settings.</p> Conclusions <p>RATS significantly reduces the risk of conversion, particularly in anatomically or nodally complex cases, without increasing vascular complications.</p>