Sustainability has increasingly become a key area of research in implementation science. A program’s sustainability—the extent to which it can deliver its intended benefits over time after initial funding has ended—is crucial to and is indicative of whether the program will have real utility in the community for which it was designed. Assessing and planning for sustainability is particularly critical in low-resource settings where various programs are implemented with development assistance funding from external donors, which is nearly always time-limited. While there are several sustainability frameworks, the literature is limited with regards to availability of a validated tool with demonstrated quantifiable benefits for program implementation in low-resource settings. Low- and middle-income countries (LMICs) in Sub-Saharan Africa (SSA) are used to represent low-resource settings in this dissertation project. For the project, I explore the policy problem in the first three chapters and present a solution in the final two chapters. First, I use system maps of two programs to depict the current context for funding and implementation of public health programs in SSA. Next, I demonstrate the impact of shifts in funding on population outcomes by looking at antiretroviral treatment (ART) coverage for HIV in SSA. Then, I present a targeted literature review on determinants of sustainability in the SSA setting. Based on these findings, I identify the program sustainability assessment tool (PSAT) as an appropriate fit and adapt it to the SSA setting based on key informant interviews. Finally, I use psychometric assessments based on a broader pilot survey to evaluate the tool’s quality in terms of reliability and validity.