Financial incentives have been widely studied and implemented as instruments to encourage healthy behavior. This narrative expert review synthesizes evidence from 39 systematic, meta-analytic, narrative, and scoping reviews examining incentive-based interventions for four health behaviors: physical activity, smoking cessation, vaccination, and medication adherence. The reviewed studies encompass a wide range of populations and contexts, though the evidence is primarily in high-income settings, with less representation from low- and middle-income countries. Across domains, financial incentives tend to produce modest, often short-lived improvements; greater effectiveness is observed when incentives are substantial, promptly delivered, and contextually tailored and when behavioral outcomes are tracked using objective measures. Targeted incentives may reduce disparities in health behavior, though their ethical and social acceptability merit careful consideration. Gaps in the literature include short follow-up windows and limited cost-effectiveness data. Future research should probe long-term outcomes, explore heterogeneity of response to better understand mechanisms of sustained change, and study the effects of nonfinancial or social incentives.