Background. Paranoia in adolescents is common, but research on attenuating it is scarce. Focusing on values and enhancing value-based acts is a low intensity method for attenuating paranoia in adults. This randomised trial compared a brief (30-minute, self-directed) values-plus-goals intervention to an active control for adolescents with high nonclinical paranoia (Paranoia Scale ≥ 53), delivered in schools. The study also investigated the role of self-esteem. Methods. Ninety adolescents were randomly assigned to condition. Paranoia (primary outcome) and self-esteem (potential mediator) were assessed at baseline (T1), and two- (T2) and six-weeks (T3) after baseline. Results. Results were analysed using intention to treat (ITT) and per protocol (PP) analysis. Using ITT analysis, the Condition*Time interaction was significant (F(2, 168) = 3.98, p = .02), paranoia was significantly lower at T3 following values-plus-goals as compared to control (d = 0.64). Differences were not significant using per protocol analysis (F(2, 106) = 1.61, p = .21). The between group effect size at T3 was (d = 0.61). The Condition*Time interaction for self-esteem was not significant (F(2, 112) = 2.86, p = .06). Conclusions. Tentatively, findings suggest that a brief values-plus-goals intervention can reduce paranoia in adolescents relative to an active control.