Objective: The purpose of this randomized, controlled trial was to examine the effects of a psychoeducational information website on improving work engagement among individual workers with low work engagement, where work engagement was measured as a secondary outcome. Methods: Participants were recruited from registered members of a web survey site in Japan. Participants who fulfilled the eligibility criteria were randomly allocated to intervention or control groups. Immediately after the baseline survey, the intervention group was invited to study a psychoeducational website called the "UTSMed," which provided general mental health literacy and cognitive behavioral skills. Work engagement was assessed by using the Utrecht Work Engagement Scale at baseline, 1-, and 4-month follow-ups for both intervention and control groups. An exploratory analysis was conducted for a subgroup with low (lower than the median scores) work engagement scores at baseline. Results: A total of 1,236 workers completed the baseline survey. In the low work engagement subgroup, a total of 313 and 300 participants were allocated to an intervention and control group, respectively. In the high work engagement subgroup, 305 and 318 participants were allocated to an intervention and control group, respectively. The program showed a significant effect on work engagement (t = 1.98, P = 0.048) at the 4-month follow-up in the low work engagement subgroup, with a small effect size (d = 0.17). Conclusion: A web-based psychoeducation resource of mental health literacy and cognitive behavioral skills may be effective for improving work engagement among individual workers with low work engagement.