Web-based interventions hold great promise for the dissemination of best practices to clinicians, and investment in these resources has grown exponentially. Yet, little research exists to understand their impact on intended objectives.The Post-Traumatic Stress Disorder (PTSD) Clinicians Exchange is a website to support clinicians treating veterans and active duty military personnel with PTSD, evaluated in a randomized controlled trial (N = 605). This manuscript explores how a subset of clinicians, those who utilized the intervention (N = 148), engaged with it by examining detailed individual-level web analytics and qualitative feedback. Stanford University and New England Research Institutes Institutional Review Boards approved this study.Only 32.7% of clinicians randomized to the intervention ever accessed the website. The number of pages viewed was positively associated with changes from baseline to 12 months in familiarity (P = 0.03) and perceived benefit of practices (P = 0.02). Thus, engagement with the website did predict an improvement in practice familiarity and benefit outcomes despite low rates of use.This study demonstrates the importance of methodologically rigorous evaluations of participant engagement with web-based interventions. These approaches provide insight into who accesses these tools, when, how, and with what results, which can be translated into their strategic design, evaluation, and dissemination.