The rapid growth of digital payment systems in India, particularly the widespread adoption of Unified Payments Interface (UPI), has significantly transformed the transaction landscape for small-scale retailers. This study aims to examine the factors influencing digital payment adoption among small retail vendors in Bangalore, with a specific focus on behavioural intention and the continued relevance of traditional payment methods. Primary data were collected from small-scale retail business vendors using a structured questionnaire, focusing on their usage, perception, and adoption of UPI-based payment systems. The study employs Partial Least Squares Structural Equation Modelling (PLS-SEM) to analyse the measurement and structural models. Reliability and validity assessments indicate strong internal consistency, with Cronbach’s Alpha and Composite Reliability values exceeding the recommended thresholds, and Average Variance Extracted (AVE) confirming adequate convergent validity. The structural model results reveal a significant positive relationship between traditional payment methods and digital payment adoption (β = 0.393, p < 0.001), suggesting a complementary coexistence rather than substitution. Interestingly, behavioural intention shows a significant but negative relationship with digital payment adoption (β = -0.174, p < 0.05), indicating a potential intention–behaviour gap among retailers. Furthermore, the relationship between traditional payment methods and behavioural intention is found to be statistically insignificant (p > 0.05). The findings highlight that while UPI adoption is increasing, actual usage behaviour among small retailers is influenced more by practical and contextual factors than by intention alone. The study contributes to the growing literature on digital financial inclusion by emphasizing the hybrid nature of payment systems in emerging markets. It also provides implications for policymakers and fintech stakeholders to focus on infrastructure development, trust-building, and user-centric solutions to enhance digital payment adoption.