BACKGROUND: Digital payment systems are pivotal in the digital economy, relying on the interplay between internet technology and e-vendors. While the Technology Acceptance Model (TAM) and the Theory of Planned Behavior (TPB) have been extensively used to explain technology adoption, the role of trust in financial technology adoption remains underexplored. This study addresses this gap by developing an extended Trust-TAM-TPB model, providing a comprehensive framework to analyze digital payment adoption in emerging markets. METHODS: A quantitative approach was adopted, analyzing survey data from 509 respondents using Structural Equation Modeling (SEM). The extended model examines both technological factors (perceived usefulness, perceived ease of use) and trust-related factors (trust's influence on behavioral intention via subjective norms, attitude, and perceived behavioral control). RESULTS: Findings confirm that trust is a significant determinant of digital payment adoption, influencing both perceived usefulness and subjective norms. However, a negative relationship was found between perceived usefulness (PU) and attitude (ATT), suggesting that while users recognize the benefits of digital payments, their attitudes may still be shaped by traditional cash-based habits and security concerns. These insights challenge traditional TAM assumptions and emphasize the importance of trust in driving adoption. CONCLUSIONS: This study contributes to technology acceptance literature by integrating trust into the TAM-TPB framework and highlighting its dual role in shaping both perceived usefulness and behavioral intention. Practically, the findings suggest that policymakers and financial institutions should prioritize trust-building strategies, including fraud prevention measures, financial literacy programs, and transparent transaction policies, to accelerate digital payment adoption in developing economies. These insights are particularly relevant for Vietnam's Northern mountainous regions, where digital payment penetration remains low.