Background <p>Adolescence is a crucial developmental period characterized by increased challenges in emotion regulation, a key mechanism linked to mental health. In Kenya, one in every two adolescents and youth faces a mental health challenge, highlighting a need for early interventions targeting emotion regulation. This study will evaluate the efficacy and acceptability of MAISHA, a blended indicated mental health intervention co-designed with young people to strengthen emotion regulation among those experiencing related difficulties.</p> Methods <p>In a parallel group, cluster-randomized 2 × 2 factorial controlled trial, 666 young people aged 13–25 will be randomly allocated to one of four 4-week study arms at a ratio of 1:1:1:1. (1) digital app blended with a face-to-face element; (2) digital app only; (3) face-to-face element only; or (4) care as usual (CAU). The digital app will build on an ecological momentary intervention. The face-to-face element will consist of four group sessions on growth mindset, values, and gratitude. The primary outcome is emotion regulation difficulties, assessed post-intervention using the short form of the Difficulties in Emotion Regulation Scale (DERS-SF), and comparing the blended intervention (digital and face-to-face) to CAU. Secondary measures include emotional reactivity, emotional distress, positive and negative affect, acceptability, desirability, safety, and usability. The trial will include an embedded micro-randomized trial and a process evaluation.</p> Discussion <p>This trial advances adolescent global mental health by strengthening evidence on youth-focused, mechanism-informed, blended interventions while also highlighting participatory approaches in LMICs.</p> Trial registration <p>The trial was registered in the Pan African Clinical Trials Registry on July 17th, 2025, as PACTR202507903096871 (<a href="https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=34896">https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=34896</a>).</p>