Stage III lung cancer (LC) represents a heterogeneous group of diseases, and the optimal management is still a matter of debate. To date, only a few studies have assessed the role of multidisciplinary team (MDT) discussion in impacting survival of stage III LC. Hence, we aimed to reported the impact of the implementation of MDT discussion on long-term survival of stage III LC patients. This is a retrospective, observational, single-centre cohort study evaluating data of consecutive patients with a clinical and pathological diagnosis of stage III LC treated before [2005-2011] and after [2012-2020] the implementation of MDT. The primary outcome was 5-year overall survival (OS). A total of 983 patients were enrolled with stage III LC, 411 (41.8%) pre-MDT and 572 (58.2%) post-MDT. The 5-year OS rates were 25.3% for the pre-MDT cohort and 33.9% for the post-MDT cohort (P=0.0008). Resected patients (n=670), who underwent trimodality therapy achieved a higher 5-year OS in both pre-MDT and post-MDT groups. An increased 5-year OS was observed in patients who underwent systemic therapy, from 28.2% in pre-MDT to 40.2% in post-MDT cohorts. In non-resected patients, there was an increased in 5-year OS in both systemic and chemoradiotherapy groups. The implementation of an MDT increased the 5-year OS in both resected and non-resected stage III LC patients. Implementing MDT might be useful in improving the management of therapy with less invasive local and surgical strategies personalized for each LC patient.