This study examines the combined impact of FinTech adoption (FA), green finance (GF), and financial literacy (FL) on sustainable consumer behaviour (SCB) in the Indian digital financial landscape. It further scrutinises the mediating role of financial literacy in the transformation of the digital financial engagement and green financial awareness into sustainability-oriented behavioural outcomes. A quantitative cross-sectional design was adopted whose results were based on the survey data collected from 430 active users of financial digital services in both urban and semi-urban areas in India. Partial Least Squares Structural Equation Modelling (PLS-SEM) was used through the software Smart PLS 4.0 to measure construct reliability, convergent and discriminant validity, structural relationships and indirect mediation relationships. The analysis supports strong psychometric properties on all constructs and find that both FA and GF significantly improve on FL as well as on SCB. Green finance has a large predictive relevance of FA, FL, and SCB. Financial literacy was a powerful mediator in the relationships of the FA - SCB and the GF - SCB, which evidenced meaningful indirect and sequential mediation effects. The structural model has a high explanatory power the model explains 69.2% of the variance in sustainable consumer behaviour (R² = 0.692)., thus shedding light on the important role of literacy and awareness to promote sustainable financial behaviour. This research adds an integrated model linking the financial technology utilization, green financial orientation and financial capability towards sustainability driven consumer behaviour which is an underexplored area in emerging economies. The findings provide valuable information for immediate action, for policymakers, educators, and FinTech providers looking to enhance sustainability outcomes using digital financial ecosystems.