Psychosis is a severe mental health condition that is highly stigmatized, significantly increasing the costs of mental healthcare and reducing the productivity of those affected. Due to public stigma, individuals with psychosis often delay seeking professional help, exacerbating the socioeconomic burden of their ill-health. Psychoeducation, delivered in a structured and systematic manner, has been a key part of evidence-based psychological treatments and has been gradually adopted in stigma reduction efforts. This study evaluated the effectiveness of a digital single-session cognitive behavioral psychoeducation intervention in reducing public stigma toward people with psychosis in a collectivist society through a randomized controlled trial. Stigma was assessed using standardized self-report tools at pre-intervention, post-intervention, and 1-month follow-up. A significant reduction was observed in stereotyping, prejudice, and discrimination on seven out of 10 public stigma components post-intervention. However, the desired effects were maintained for only two components at the 1-month follow-up. No significant changes were found in negative emotions, tolerance, and support from pre-intervention to post-intervention. Attribution of responsibility significantly increased after the intervention, contrary to predictions. The findings of this study provide empirical support for the short-term effectiveness of a brief cognitive behavioral psychoeducation intervention in reducing public stigma toward individuals with psychosis while highlighting the potential benefits of delivering this intervention digitally. At the same time, the limitations of individual-level interventions in sustaining long-term effects are discussed from a sociocultural perspective. This study also examined the relevance of these findings in the context of health economics.