The mhGAP guideline supports countries to strengthen capacity to deal with the growing burden of mental, neurological and substance use (MNS) conditions and narrow the treatment gap. This new edition includes 30 updated and 18 new recommendations, alongside 90 pre-existing recommendations. This is the third iteration of the guideline and reflects 15 years of investment in the mhGAP programme. The revised recommendations ensure that mhGAP continues to offer high-quality, timely, transparent, and evidence-based guidance to support non-specialist health workers in low-income and middle-income countries in providing treatment and care to individuals with MNS conditions.