ABSTRACT The burden mental, neurological, and substance (MNS) disorders in low-and middle-income countries (LMICs) is tremendous, but solutions for addressing the MNS burden remain limited in global adolescent mental health research. The rapid growth and widespread use of technology has the potential to address MNS burden by offering new solutions for transforming services; however, e-Health has not been systematically studied for preventive mental health intervention in LMICs. This proposed two-phase R21/R33 study seeks to respond to the growing burden of adolescent MNS disorders and urgent preventive service needs in LMIC by testing usability, feasibility (R21 phase) and effectiveness (R33 phase) of a mHealth intervention, mHealth Toolkit for Screening & Empowering Lives of Youth (mSELY), to promote adolescent mental health in Kenya. The mSELY is a preventive intervention tool to be used by adolescents and/or their caregivers as a self-help support modality. The mSELY-A is designed for adolescents and mSELY-P is designed for parents/caregivers. The mSELY integrates 4 key mental health service functions: i) comprehensive screening for adolescent social-emotional/mental health and relevant risks (in multiple RDoC domains); ii) a strength and weakness profile for an adolescent’s behaviors; iii) tailored mental health literacy and promotion strategies, and iv) tailored referral resources. To promote accessibility and to have broader reach, the mSELY will be embedded in diverse community based organizations (CBOs) that already provide services to adolescents. In addition, a youth empowerment approach of task-shifting will be applied to train a team of adolescent-peer-community- health workers (A-CHWs) to support the mSELY implementation. This project is conceptualized within the Social Action Theory, mHealth/Technology Acceptance Model, and Implementation Outcomes Framework. The specific aims are: (1) to build research and service capacity for digital and public health approaches of adolescent mental health promotion; (2) to employ a user-centered design to test and enhance usability of the mSELY-A and P (in R21 Year 1) and to test feasibility and efficacy of mSELY-A alone, mSELY-P alone, and combination of mSELY-A + P in youth-served CBOs; (3) to test the effectiveness of the optimized versions of mSELY-A and P using a cluster-randomized control trial (cRCT); and 4) to disseminate and explore big data analytic approaches using the Toolkit data to improve Digital-Toolkit decision support functions and accuracy of mental health precision care.