Abstract
The rapid growth of fintech in Indonesia has improved access to digital financial services, but this has not automatically translated into more responsible financial behavior, particularly among Millennials balancing family, credit, and career obligations. This study examines how social capital influences responsible financial behavior among Millennials in Pontianak City, both directly and through the mediating roles of self-control and fintech adoption. A quantitative survey was distributed to Millennial respondents (born 1981–1996) domiciled in Pontianak, yielding 205 valid responses, analyzed using Structural Equation Modeling-Partial Least Squares (SEM-PLS). The results show that social capital significantly and positively influences self-control, fintech adoption, and responsible financial behavior directly, while self-control and fintech adoption jointly and sequentially mediate the effect of social capital on responsible financial behavior. All six hypothesized relationships were statistically supported. The findings indicate that fintech adoption serves as a behavioral mechanism through which social and psychological capital translate into financial conduct, with self-control playing the dominant mediating role. These results extend behavioral finance literature to an underrepresented regional and generational context and offer practical implications for fintech providers, financial educators, and policymakers seeking to strengthen responsible financial behavior among Millennials.