This policy brief draws on lessons learned from a recent post-project sustainability study (PSS) of a community health project in Indonesia. Understanding how project components and results are evolved, sustained, and adopted after the conclusion of a project is important from policy perspective as the lessons learned serve to inform future programming, as well as contribute to the general body of knowledge. The paper suggests that the focus of any PSS should not only examine what activities are sustained, but also the factors responsible for sustaining the results. It also suggests that, mixed methods – quantitative and qualitative – help research teams understand why and how project activities are sustained. It further suggests that PSSs are different from traditional impact evaluations, so including all of the stakeholders in the study is crucial in order to understand how they contributed toward the project’s sustainability. Other conclusions related to sustainable development goals (SDGs) are also made.