The high rates of anxiety in college students and the many barriers to accessing evidence-based care in communities and on campuses indicate a clear need to explore ways to provide effective evidence-based treatments to more people. Web-based interventions and preventions are one way to bridge this gap, and hold the potential to decrease suffering and mental health disparities. The current randomized control trial examined the acceptability and efficacy of a three-session web-based therapist assisted acceptance-based behavioral intervention targeting anxiety (Surviving and Thriving During Stress, SATDS) for college students versus a waitlist (WL) control condition, in a sample of diverse college students. Overall, participants rated the program as helpful and acceptable. Mixed-model repeated-measures (MMRM) models were run in SPSS to examine the effects of time, condition, and condition x time on outcomes and mechanisms. Results indicated there were significant condition x time interactions for general anxiety, depression, and quality of life (QOL); indicating SATDS participants reported significantly greater changes on these outcomes from pre- to post- treatment vs. WL. MMRM models examining hypothesized mechanisms of change indicated there were significant condition x time interactions for experiential avoidance and decentering, and a marginally significant interaction for valued living. Bivariate correlations between residualized gain scores on both outcomes and mechanisms affected by the intervention indicated that change in mechanisms was generally associated with change in outcomes. All significant gains were maintained at one-month follow-up, with the exception of QOL. Results contribute to the growing literature on the acceptability and efficacy of web-based approaches, and suggest that these approaches can be effective for diverse college students, and may provide a unique platform to increase access to evidence-based care. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]