Objectives: The Working Mind is a program designed to reduce stigmatizing attitudes toward mental illness, improve resilience, and promote mental health in the general workplace. Previous research has revealed positive program effects in a variety of workplace settings. This study advances previous work in implementing randomization and a control group to assess the intervention’s efficacy. Methods: The program was evaluated using a cluster-randomized design, with pretest, posttest, and a 3-month follow-up in 2 implementation groups across 4 sites. Results: The Working Mind program was effective at decreasing mental health stigma and increasing self-reported resilience and coping skills at the pre–post assessment in both delivery groups. The program’s effects were maintained to the time of 3-month follow-up. Qualitative data provided further evidence that participants benefited from the program. Conclusions: This study represents an advancement over past research and provides further support for efficacy of the Working Mind program. Directions for future research, including replication using rigorous methodological procedures and examination of program effects over longer follow-up intervals, are discussed.