Background: High levels of self-stigma are associated with a range of adverse mental health, treatment, and functional outcomes. This prospective study examined the effects of an electronic mental health stigma reduction intervention on self-stigma (self-blame, shame, and help-seeking inhibition) among male construction workers in Australia. Method: Male construction workers (N = 682) were randomly assigned to receive either the intervention condition or the wait list control over a six-week period. Self-stigma was assessed using the Self-Stigma of Depression Scale at post-intervention. We conducted linear regression to assess the effectiveness of the intervention on self-stigma, adjusting for relevant covariates. Results: Self-stigma was relatively low in the sample. The intervention had no significant effect on self-stigma, after adjusting for confounders. There were reductions in stigma in both the intervention and control groups at 6-week follow-up. Process evaluation indicated that participants generally enjoyed the program and felt that it was beneficial to their mental health. Conclusions: These observations underscore the need for further research to elucidate understanding of the experience of self-stigma among employed males.