A randomized controlled trial of 1,025 Australians found that receiving personal genomic risk information for melanoma improved prevention behaviors through specific psychological mechanisms. Among high-risk participants, genetic testing increased sun protection at one month, mediated by enhanced perceived importance and effectiveness of protection strategies. In women, the intervention boosted whole-body skin examinations through increased perceived capability and control over melanoma detection. These findings illuminate how precision medicine interventions work psychologically. Rather than genetic information directly changing behavior, it appears to operate through empowerment pathways—people feel more capable and in control when armed with personal risk data. This suggests that genetic testing's value may lie not just in risk stratification, but in its psychological impact on health agency. The research addresses a critical gap in precision prevention: understanding the 'black box' between genetic information and behavior change. However, the study focused on Australians of European ancestry, limiting generalizability to diverse populations. As this is a preprint awaiting peer review, these mechanistic insights require validation before informing clinical practice or genetic counseling protocols.