Introduction Improving the sustainability of public health interventions is a priority for policymakers and program implementers. However, existing theories, models, and frameworks focus on describing constructs, processes, and measures of sustainability. Models to guide the improvement of sustainability of public health interventions are currently lacking. Objective To develop an evidence-based model that can systematically guide the improvement of the sustainability of public health interventions. Methods We used a systematic and multi-stage approach to iteratively develop the model. A narrative review of the sustainability literature identified key constructs relevant to the improvement mechanisms of sustainability. Identified constructs were then developed into stages and activities. We applied the resulting model to guide development of improvement strategies in four public health interventions in Southeast Asia, verifying the applicability of the model to real-life contexts.