This study examines the mechanisms fostering sustainable value propositions of implemented e-Governments projects in sub-Saharan Africa (SSA) as a research focus. Value propositions identify how public organizations use e-Government to fulfill citizens' needs across different roles. Using a concept-centric systematic review, we identified such value propositions as effective public organizations, quality service delivery, open government and democratic values, as well as social values and well-being. We chose some selected e-Government projects in Nigeria and Rwanda; adopted realist evaluation (RE) multiple case studies as a methodology and introduced affordance actualization, self-determination theory, and sustainability framework for e-Government success as theoretical lenses. To collect data, we adopted a mixed method RE approach and used a contingent valuation method (CVM) as a quantitative aspect to identify the actualized value propositions in operations in the implemented e-Government projects in Nigeria and Rwanda as outcomes. Sequentially followed by a realist interview as a qualitative approach to collect and analyze data we uncovered the generative mechanisms causing such outcomes to exist and be sustainable. Our findings revealed technological cognizance and autonomy as well as competence as individual mechanisms identified for sustaining such outcomes. While organizational mechanisms revealed are continuous availability of funds, institutional, administrative, and coordinating capacity with leadership and political support. Other organizational mechanisms include institutionalizing the technology within local settings with ongoing monitoring and improvement evaluation enabled by both internal and external contextual conditions. We synthesized our findings into an actualized value sustainability framework for implemented e-Government projects in SSA to contribute to academics and practice in ICT4D, particularly RE application in e-Government study, which is nascent.