Web courses for evidence-based treatments (EBTs) are an important component of training models and broader treatment dissemination and implementation. However, there exists limited research on the efficacy of large-scale online training, as most studies exploring these trainings focus on web courses designed for a specific research project. This project explored participation and knowledge acquisition in two large-scale web courses for trauma-focused EBTs: TFCBTWeb2.0 and CPTWeb2.0. Data were extracted for 174,193 TFCBTWeb2.0 learners and 12,024 CPTWeb2.0 learners, including learner characteristics (e.g., degree, years of experience) and knowledge acquisition from course module pre- and posttest scores. Learners demonstrated significant increases in knowledge for all TFCBTWeb2.0 and CPTWeb2.0 modules. Examination of completion status (i.e., started vs. completed the course) indicated that learners who identified as trainees or early career professionals were more likely to complete a web course, compared to those with terminal degrees and 5+ years of experience. Learners who registered for TFCBTWeb2.0 prior to the COVID-19 pandemic also had slightly higher completion rates compared to peri-COVID-19 learners. Taken together, these findings suggest that web courses can be an effective tool for increasing EBT knowledge. Further, completion rates for both web courses suggest the potential importance of system-level factors (e.g., agency/supervisor support) to increase the likelihood of completing these types of trainings.