This study examines the impact of mobile and internet banking on the financial performance, operational efficiency, and sustainability practices of small and medium-sized enterprises (SMEs) in Oman. Despite rapid digital transformation initiatives in the Gulf region, there remains limited empirical evidence on how FinTech adoption affects SME outcomes in emerging economies. Drawing on a multilingual survey of 125 SME owners and guided by four established technology adoption theories—TAM, UTAUT, TTF, and DOI—the research tests four hypotheses using logistic and ordered logistic regression models. The results indicate that mobile banking availability is significantly associated with improved financial performance. However, usage frequency alone does not yield statistically significant performance gains, suggesting that access is a necessary but insufficient condition. For operational efficiency and sustainability, mobile banking access demonstrates a positive effect in simpler models, but firm-level characteristics—particularly size and usage intensity—emerge as stronger predictors in multivariate analysis. These findings highlight the importance of strategic digital engagement rather than passive adoption. This study contributes to the FinTech literature by offering theory-driven evidence from an underrepresented regional context and emphasizing the role of behavioral and organizational factors in realizing the benefits of digital finance. It also provides practical insights for policymakers aiming to foster inclusive, sustainable SME ecosystems through targeted digital finance initiatives.