Background Mental health literacy (MHL) is an evolving concept encompassing knowledge of mental illness, help-seeking options, perceived stigma, and discrimination. This study aimed to test the effectiveness of a human library intervention at enhancing MHL. A human library intervention was adopted to enhance MHL in this study. The human library intervention aims to establish a positive framework and safe space for dialogue between readers and a ‘human book’. It works to promote dialogue, reduce prejudice, and encourage understanding of people who are regarded as disadvantaged or in a minority group. Methods An experimental approach with a multigroup pretest–posttest design was adopted. Forty-five participants aged between 18 and 23 years were recruited and randomly assigned to the experimental group (human library intervention), comparison group (didactic teaching session), or control group (no intervention). Adapted vignette-based MHL scale scores were used as the outcome measures. The overall and subscale scores were included in the analysis. Results The human library intervention group showed a significant improvement in overall MHL compared with the other two groups. In a multivariate analysis of the variance in subscale scores, the intervention was shown to significantly reduce stigma and preferred social distance, but had no significant effect on knowledge acquisition. Conclusions The human library intervention is effective at enhancing overall MHL and reducing stigma and preferred social distance. Further studies are suggested to further develop the MHL construct, human library interventions, and the MHL scales for consolidating evidence-based practice.