The Unified Payments Interface (UPI), developed by the National Payments Corporation of India (NPCI) and launched in April 2016, has emerged as a transformative force in India’s digital financial ecosystem. This empirical study examines customer satisfaction towards UPI-based applications for digital transactions and payments in Mumbai city. A descriptive research design was adopted, and primary data were collected from 50 respondents using a structured questionnaire. The study explores key dimensions including demographics, app preferences, frequency of use, satisfaction levels, perceived challenges, and willingness to recommend. Findings reveal that 96% of respondents actively use UPI, with Google Pay dominating user preference at 90%. A significant majority (87.8%) expressed satisfaction with UPI services, citing convenience, transaction speed, and 24/7 availability as primary drivers. Major challenges include network failures (36%) and pending transactions (36%). The study recommends improvements in security infrastructure, customer grievance mechanisms, and rural internet connectivity to sustain and enhance user satisfaction.