Sustainable development has emerged as a paramount priority globally, with the fintech services playing a crucial role in achieving these goals. Although previous research has explored consumer perceptions of novel fintech services, including Buy Now Pay Later (BNPL) applications, there remains a knowledge gap regarding the factors influencing adoption among young consumers. This study addresses this limitation by investigating the determinants of BNPL app usage among Saudi Arabian Generation Z consumers, integrating the Unified Theory of Acceptance and Use of Technology and DeLone and McLean’s Information Systems Success model. A survey of 380 BNPL app consumers from Generation Z was conducted, and their responses were analyzed using structural equation modeling. The findings reveal that performance expectancy, effort expectancy, and social influence positively impact the intention to continue using BNPL apps. Furthermore, system quality, service quality, and information quality exhibit significant correlations with satisfaction within the IS Success model. The study’s outcomes are expected to inform app developers in designing effective apps that engage digital-native consumers and provide policymakers with insights to enhance fintech services. This research contributes significantly to the existing body of knowledge on fintech adoption, intentions, and satisfaction.