A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was whether intraoperative conversion to thoracotomy have an impact on long-term survival for patients with non-small cell lung cancer (NSCLC) who underwent video-assisted thoracoscopic lobectomy initially? A total of 461 papers were found using the reported search, of which 6 retrospective cohort studies represented the best evidence to answer the clinical question. The authors, date of publication, journal, country of the authors, patient group, study type, relevant outcomes, and results of these papers are tabulated. Five cohort studies clarified that conversion did not compromise long-term survival, while one cohort study reported worse long-term outcomes after conversion to thoracotomy. However, the limited samples, different characteristics between groups and selection bias due to inherent design made it difficult to interpret a conclusion. Based on the current evidence, we concluded that intraoperative conversion from video-assisted thoracoscopic surgery (VATS) to thoracotomy for NSCLC might not impact long-term survival compared to successful VATS lobectomy. The in-hospital mortality might not be prejudiced, while a longer hospitalization was observed. However, whether conversion would adversely affect postoperative complication rates remained unclear because of the conflicting results. Moreover, three studies reported no statistical difference in short- and long-term survival between emergent and non-emergent conversion. Therefore, we suggest that thoracic surgeons should not hesitate to convert VATS into thoracotomy in the case of blood vessel injury or difficult hilum.© The Author(s) 2021. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery.