CONTEXT: Fiscal constraints, demographic shifts, and the growing burden of noncommunicable diseases (NCDs) challenge the sustainability of health systems. Innovative financing instruments, such as social impact bonds (SIBs), have been proposed to support prevention and health promotion, yet empirical evidence on their effectiveness remains limited. OBJECTIVES: To explore the advantages and disadvantages of SIBs for financing health prevention and promotion in OECD countries, drawing on perspectives from key stakeholders and evidence from the scientific and grey literature. DESIGN: We conducted a qualitative exploratory study combining 15 semi-structured interviews with academics, consultants, investors, and representatives of public institutions, and a targeted review of 21 publications identified through a PubMed search and supplementary grey literature sources. Thematic analysis was applied to interview transcripts using a mixed inductive-deductive coding approach, and findings were triangulated with literature evidence. RESULTS: SIBs offer flexibility in service delivery, foster performance monitoring, and may provide longer-term financial stability to service providers. They support the piloting of innovative interventions and enhance accountability in program implementation. However, expected cost savings for governments were rarely realized in practice. Concerns have also been raised, mainly in the theoretical literature, about rigid outcome targets, limited empirical evidence of effectiveness in NCD prevention, high transaction costs, the "wrong pocket" problem, and political vulnerability. In practice, while SIBs are considered more suitable for narrowly defined interventions with measurable intermediate outcomes than for population-wide prevention programs, their scale-up is possible, for example though outcome funds-pooling multiple SIB projects-were viewed as a potential solution for attracting larger investors and creating broader impact. CONCLUSIONS: SIBs offer a promising but contested approach to financing prevention and health promotion. Their success depends on careful intervention selection, transparent design, and adaptation to local institutional and political contexts. CLINICAL TRIAL NUMBER: Not applicable.