The aim of the study was to estimate the efficiency of a peer-based teaching and cooperative learning intervention in forensic users with a complex neurodivergent profile (Autism Spectrum Disorder, Attention-Deficit/Hyperactivity Disorder, and intellectual disabilities). The research question was that peer-facilitated learning would increase social communication, emotional regulation, engagement, and self-efficacy and decrease behavioral incidents as compared to usual clinician-facilitated interventions. The quasi-experimental mixed-methods study design was used, including 84 adult forensic service users who were divided into a collaborative learning group (led by peers, n=42) and a control group (led by a clinician, n=42). Psychosocial measurements and institutional behavioral records were used to measure outcomes at a 12-week post-intervention point and six months of follow-up to evaluate the effect of the intervention. There were repeated measures ANOVA, regression, and mediation analyses. Social communication (F (2,162) = 8.94, p < 0.001) and emotional regulation (F (2,162) = 7.63, p <0.01) had significant time x group interaction effects. Big effect sizes in the post-test (Cohen’s d = 1.21 and d = 1.08, respectively) and the gains at follow-up were found. Incidents of behavioral engagement were a significant predictor of behavioral incident reductions (β = −0.42, p < 0.01). The peer-led group showed a 56% decrease in behavioral episodes as compared to 15% in the control group, and continued to improve after six months. Collaborative learning led by peers had a considerable positive impact on socio-emotional functionality and minimized the behavioral risk of neurodivergent forensic service users. Their results suggest the incorporation of neurodiversity-informed, peer-mediated methodology into the context of forensic rehabilitation to promote responsivity, engagement, and desistance in the long run.