Objective: The aim of this study is to establish evidence to support the validity of a novel faculty-resident intraoperative assessment tool for entrustment known as OpTrust. Background: Recently, the landscape of surgical training has been altered, in part, because of resident work-hour changes and increased supervision requirements. To address these concerns, a new model for assessment of teaching and learning in surgical residencies must be anchored on progression through milestones and entrustment. Methods: OpTrust was designed to assess the faculty-resident dyad in the operating room and measure the entrustment exhibited during intraoperative interactions across 5 domains: (i) types of questions asked, (ii) operative plan, (iii) instruction, (iv) problem solving, and (v) leadership by the surgical resident. After initial pilot testing and refinement of OpTrust, 5 individual raters underwent rater training sessions; 49 individual operating room observations were completed based on 28 cases. Results: OpTrust, as a tool for assessing intraoperative entrustment, is supported by strong validity evidence. In part, it demonstrates strong interrater reliability across all faculty domains as measured by intraclass correlation 1 (ICC1) (0.81-0.93). For resident domains the results were similar with ICC1 (0.84-0.94). Cronbach alpha was 0.89 and 0.87 for faculty and resident entrustment respectively, signifying the 5 domains could be combined into a single construct of entrustment. A high correlation existed between faculty and resident scores (Pearson r = 0.94, P < 0.001) indicating a strong positive linear relationship between faculty and resident mean entrustment scores across all scale domains. Conclusions: OpTrust successfully assesses behaviors associated with entrustment during intraoperative faculty-resident interactions, and has the potential to be adopted across other procedural-based specialties to promote autonomous training progression.