Aim: Unlike medication treatment, which may confer an unfavourable risk-benefit ratio, psychosocial intervention has been an emerging target of recent randomized controlled trials (RCTs) assessing its efficacy in delaying or preventing the onset of psychosis in individuals identified at 'clinical high risk'. Literature comparing qualitative differences in these psychotherapeutic interventions is scarce. The aim of the current study was to conduct a PRISMA systematic review evaluating the efficacy of psychotherapeutic interventions in reducing the rates of conversion to psychosis in clinical high-risk individuals. Methods: RCTs were identified in PubMed, Medline and PsycINFO databases up to 30 November 2013. Six studies (comprising 800 participants) met review inclusion criteria. Three investigators performed data extraction independently by using a pre-structured selection form, and conducted risk of bias assessment employing the Cochrane approach. Results: All six studies employed cognitive behaviour therapy as a core element. Three trials achieved a significant effect. The two trials that employed cognitive behaviour therapy enhanced for the specialized needs of clinical high-risk patients maintained significant effects at post-treatment follow up. Conclusion: Evidence from recent trials suggest that cognitive behaviour therapy may be beneficial in delaying or preventing onset of psychosis in clinical high-risk individuals, although effect sizes to date appear small. Further research is needed in larger samples to establish whether cognitive behaviour therapy is efficacious, and if additional intervention components can enhance established psychotherapies. Keywords: adolescent; adult; psychotherapy; psychotic disorder; review.