Sarcomas are rare but aggressive diseases. Specialized multidisciplinary management is not implemented for all patients in most countries. We investigated the impact of a multidisciplinary tumor board (MDTB) presentation before treatment in a nationwide study over 5years. NETSARC (netsarc.org) is a network of 26 reference sarcoma centers with specialized MDTB, funded by the French National Cancer Institute to improve the outcome of sarcoma patients. Since 2010, presentation to an MDTB and second pathological review are mandatory for sarcoma patients in France. Patients’ characteristics and follow-up are collected in a database regularly monitored and updated. The management and survival of patients presented to these MDTB before versus after initial treatment were analyzed. Out of the 12528 patients aged ≥15years, with a first diagnosis of soft tissue and visceral sarcoma obtained between 1 January 2010 and 31 December 2014, 5281 (42.2%) and 7247 (57.8%) were presented to the MDTB before and after the initiation of treatment, respectively. The former group had generally worse prognostic characteristics. Presentation to a MDTB before treatment was associated with a better compliance to clinical practice guidelines, for example, biopsy before surgery, imaging, quality of initial surgery, and less reoperations (all P<0.001). Local relapse-free survival and relapse-free survival were significantly better in patients presented to a MDTB before initiation of treatment, both in univariate and multivariate analysis. The compliance to clinical practice guidelines and relapse-free survival of sarcoma patients are significantly better when the initial treatment is guided by a pre-therapeutic specialized MDTB.