HIV prevalence remains high in Zanzibar, Tanzania, despite comprehensive prevention efforts. A cluster randomized controlled trial design was employed to assess the impact of peer educators delivering HIV prevention messages versus standard care controls. A total of 500 participants were randomly assigned to either a control group or an intervention group, with baseline and follow-up assessments conducted over one year. Peer education significantly increased knowledge about HIV transmission methods by 20% in the intervention group compared to the control group (p < 0.05). The peer education programme was effective in improving young adults' understanding of HIV prevention strategies, though further research is needed to explore sustained behaviour change. Continued support for peer educators and ongoing educational campaigns are recommended to maintain knowledge gains among the population. HIV Prevention, Peer Education, Young Adults, Zanzibar, Tanzania Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.