Background The Mental Health Gap Action Programme (mhGAP) supports engagement of non-specialists in mental health services in Low- and Middle-Income countries. Given this aim, assessment of the effectiveness of approaches under its remit is warranted. Aims We evaluated mhGAP approaches relating to child and adolescent mental health, focusing on provider / child outcomes, and barriers / facilitators of implementation. Methods Thirteen databases were searched for reviews and primary research on mhGAP roll out for child and adolescent mental health. Results Twelve studies were reviewed. Provider-level outcomes were restricted to knowledge gains, with limited evidence of other effects. Child-level outcomes included improved access to care, enhanced functioning and socio-emotional well-being. Organisational factors, clients and providers? attitudes and expectations, and transcultural considerations were barriers. Conclusions Further attention to the practical and methodological aspects of implementation of evaluation may improve the quality of evidence of the effectiveness of approaches under its remit.