This study examines the psychological, sociological, and technological factors that influence impulsive buying behavior and the adoption of pay later among Indonesian e-commerce consumers. Although BNPL is growing rapidly, there are still concerns about how it normalizes financial risk and impulsive spending among young consumers. Data was collected from 357 digitally skilled individuals in Jakarta, Bogor, Depok, Tangerang, and Bekasi (cities in Indonesia) through purposive sampling and online surveys between March 8 and April 10, 2025. The participants were person who has experience using pay later. Generation Z and consisted of students, private sector workers, and business owners. Built on six variables, the paradigm of this study allows for seven hypotheses to be made to explore the relationships between these components. SmartPLS 4 analysis shows that social influence, self-control, and happiness are the main drivers of impulsive buying, which in turn strongly predicts the acceptance of pay later. While trust and ease of use have little influence, satisfaction also helps increase the intention to adopt. These results challenge traditional fintech adoption theory by demonstrating the superiority of psychological and social drivers over functional characteristics in the use of pay later. The results of this study encourage fintech developers to integrate behavioral nudges that reduce impulsive spending and policymakers to prioritize financial literacy programs tailored to the digital-native demographic. By addressing the interaction between deferred payment systems and consumer psychology, this study provides actionable insights to promote responsible BNPL usage in emerging markets.