The rapid growth of financial technology in Fintech has transformed the perspective and the way how individuals participate in financial markets. The emergence of digital trading platforms, Robo-advisor service, mobile investment applications and AI -driven Analytics has significantly increased retail investor participation, particularly in emerging economies like India. According to NSDL and CDSL reports 2024, India has crossed 100 million demat accounts, indicating a structural farmwork shift towards technology-enabled study. Even if there is a rapid growth in technology, there is a limited conceptual clarity exist regarding how fintech usage influences individual investment decision-making, especially through the lens of behavioural finance and technology adoption theories. This paper integrates the technology acceptance model (TAM), Unified theory of acceptance and use of technology (UTAUT) and Behavioural Finance Theory to propose a theoretical framework explaining the relationship between investment behaviour and fintech usage. The study identifies behavioural biases as a mediating factor and financial literacy as a moderating variable. The paper contributes by offering a conceptual structured model for future empirical testing and provides implications for investors, fintech firms, and policymakers.