This study assessed knowledge attainment of healthcare professionals who participated in a nationwide sexual assault forensic examiner training program developed by the International Association of Forensic Nursing. A comprehensive curriculum was divided into 12 modules that students accessed through an online learning management system. Using a one-group pretest-posttest design, we assessed students' knowledge attainment for all 12 online modules. The results showed that the mean posttest scores were significantly greater than the mean pretest scores for all 12 online modules. On over 40% of the modules, the students exhibited at least a 25% knowledge gain. This study also examined the predictors of knowledge attainment. Using a multiple linear regression model, we found that knowledge attainment was positively associated with a reliable Internet connection, students who were drawn to the training because it was of no cost to them, and those students with higher levels of motivation. By contrast, lower knowledge gains were significantly related to students who reported more work/personal barriers and those who were drawn to sexual assault forensic examiner practice because they, or someone close to them, have personal experience with sexual assault.