This study evaluated the effectiveness of “Stigma and Mental Health: Challenges for Quality Care,” an online intervention for healthcare workers designed to reduce stigmatizing attitudes toward people with mental health problems. The participants were experienced healthcare workers in Latin America from various disciplines. Of the 77 registered participants, 55 completed the course, and the completion rate was adequate (65%). In evaluations, 60% of participants rated the intervention favorably and believed the contents were useful in promoting favorable attitudes toward people with mental health problems and substance use. Follow-up studies are required to determine the effects of the intervention at 3, 6, and 12 months after the intervention.