Abstract Objectives Medication non-adherence is a significant problem in treatment of severe mental disorders and is associated with poor clinical outcomes and increased demand on services. Task-shifting interventions incorporating mobile health may improve adherence in mental health service users in low- and middle-income countries. Seventy-seven participants were recruited from a psychiatric hospital in Cape Town, with 42 randomized to receive the intervention and 35 to treatment as usual. Intervention pairs underwent treatment-partner contracting and psychoeducation, and received monthly text message reminders of clinic appointments. Primary outcomes were intervention acceptability and feasibility. Secondary outcome for efficacy were adherence to clinic visit; relapse; quality of life; symptomatic relief and medication adherence. Results Treatment partner and psychoeducation components were acceptable and feasible. The text message component was acceptable but not feasible in its current form. Efficacy outcomes favoured the intervention but did not reach statistical significance. A treatment-partner intervention is acceptable and feasible in a low- and middle-income setting. Work is needed to ensure that additional components of such interventions are tailored to the local context. Appropriately powered efficacy studies are needed. Trial Registration PACTR PACTR201610001830190, Registered 21 October 2016 (Retrospectively registered)