A Regional Trauma Network (RTN), composed of one level I and several lower-level trauma centers (TCs) across multiple hospital systems, was established in 2010. This collaborative network used a unified triage protocol and a single transfer center. The impact of this RTN was assessed by evaluating regional mortality changes before and after RTN establishment. Patients in the state trauma registry aged 15 and older from 2006 to 2012 were analyzed; 2006 to 2009 and 2010 to 2012 were designated as pre-RTN and RTN periods, respectively. The region was defined as a county containing L1TC and its adjacent counties. Any counties bordering multiple L1TC-containing counties were excluded from analysis. Mortality was compared for all regions before and after RTN implementation. The following subgroups were also included a priori for the comparison: Injury Severity Score ≥15, age ≥65, and trauma mechanisms. 121,448 patients were analyzed; 66,977 and 54,471 patients were in the pre-RTN and RTN groups, respectively. Mean age was 58; 90 per cent had blunt injuries. The overall mortality was 4.9 per cent. Mortality comparisons over time for all regions are presented. The RTN region was the only region in the state that had mortality reduction in all patient subgroups. After adjusting for age, Injury Severity Score, level of TC that performed treatment, and trauma mechanism, RTN implementation was an independent predictor of survival (odds ratio: 0.876; 95% CI: 0.771-0.995, P = 0.04, c-statistic: 0.84). These findings suggest that regional collaboration and network-wide, uniform triage practices should be key components in the development of regionalized trauma networks.