<p>A robust body of empirical evidence suggests that forgiveness of others is positively related to individual wellbeing. However, less empirical work has been done to identify the factors that may help children not only forgive better during childhood but also develop into adults who practice forgiveness more consistently. To support a population health agenda aimed at the promotion of forgiveness, further research is needed to identify potential determinants of forgiveness. In this preregistered study, we used the first wave of nationally representative data from 22 countries included in the Global Flourishing Study (<i>N</i> = 202,898) to explore associations of 13 individual characteristics and retrospectively assessed childhood factors with dispositional forgivingness in adulthood. We estimated country-level modified Poisson models in which forgivingness was regressed on all candidate predictors, and then aggregated results for the 11 predictors that were common across countries using a random effects meta-analysis. Risk ratios from the meta-analyses showed that a combination of individual characteristics (e.g., older birth cohort, female gender), early life conditions or experiences (e.g., more frequent religious service attendance, better health, more secure family financial status), and social circumstances or influences when growing up (e.g., higher quality maternal and paternal relationships) were associated with a higher likelihood of forgivingness in adulthood. Associations were somewhat heterogeneous across the countries. Our findings suggest that childhood may be important in shaping forgivingness in adulthood and provide some potential foci for population-level interventions.</p>