Addressing the stigma of mental illness and its effect in the workplace is a contemporary issue in occupational health. The role of leaders is a vital but relatively unexplored dimension of this phenomenon. This study examined the effectiveness and application of an online intervention to reduce depression-related stigma in organizational leaders. A randomized controlled, "in the field" study was conducted with 196 leaders. Participants completed an online survey and were randomly assigned to either the experimental or wait-list control group. One week later, participants in the experimental group were given access to a brief online workplace mental health intervention and asked to complete a postsurvey, whereas the control group had to only complete the online postsurvey. Six months later, participants completed a follow-up online survey. Results revealed significant reductions in behavioral and affective depression-related stigma scores among leaders who completed the intervention, compared with the control group. These reductions were similar at 6 months. The factors that enabled or hindered training transfer from the intervention were examined through semistructured interviews with 16 of the participating leaders. Results showed that positive attitudes and high levels of knowledge are not sufficient to ensure leaders apply intervention learning in their work environments. Factors including the nature of the work environment, the collective readiness and capability of the organization to address these issues, the attitudes of others at work, and the broader political context affected the application of learning from the intervention. (PsycINFO Database Record (c) 2019 APA, all rights reserved).