Background National and subspecialty guidelines for lung and esophageal cancers recommend treatment decisions to be made in a multidisciplinary tumor board (MTB). This study prospectively analyzes the actual impact of presentation at the thoracic tumor board on decision making in thoracic cancer cases. Methods During the electronic submission process for presentation at MTB managing physicians documented their current treatment plan. The initial treatment plan was compared with the MTB final recommendation. Patient demographics, physician’s proposed treatment plan, MTB recommendation, and documentation of application of MTB recommendations were prospectively recorded in an Institutional Review Board approved database. Results Between June 2010 and December 2012, 185 patients with esophageal and 294 patients with lung cancer were presented at the MTB. One hundred sixty-six patients were presented on more than 1 occasion, resulting in 724 assessments of 479 patients. In 48 esophageal cancer patients (26%) and 118 lung cancer patients (40%) MTB recommendations differed from the initial treatment plan. Overall, a differing MTB recommendation from the primary treatment plan occurred in 330 of 724 case presentations (46%). The MTB recommendations changed treatment plans in 40% and staging and assessment plans in 60% of patients. Follow-up in a cohort of 249 patients confirmed that MTB recommendations were followed in 97% of cases. Conclusions This study validates the impact of the thoracic MTB. Recommendations will differ from the managing providers’ initial plan in 26% to 40% of cases. However, MTB recommendations can be successfully initiated in the majority of patients. Complex thoracic cancer patients will benefit from multidisciplinary review and should ideally be presented at tumor board.