Summary Points•The treatment gap for mental, neurological, and substance use (MNS) disorders is more than 75% in many low- and middle-income countries.•In order to reduce the gap, the World Health Organization (WHO) has developed a model intervention guide within its Mental Health Gap Action Programme (mhGAP).•The model intervention guide provides evidence-based recommendations developed with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology.•This article presents the management recommendations for MNS disorders, with a link to the World Health Organization website where all the background material may be accessed.•To our knowledge, this is a first exercise involving such an extensive and systematic evaluation of evidence in this area.