Behavioural finance has emerged as a critical field that challenges the traditional notion of investor rationality. This study examines the impact of cognitive biases on investment decisions among retail investors in India. Despite increasing access to financial information and technology, investor behavior often deviates from rational decision-making models due to inherent psychological tendencies. The research focuses on identifying key biases such as overconfidence, anchoring, herd behavior, and loss aversion, and assessing their influence on portfolio selection, risk perception, and trading frequency. Primary data collected through structured questionnaires from individual investors across major Indian cities is analyzed using statistical tools to determine the significance and direction of these biases. The findings reveal that cognitive biases play a substantial role in shaping investor preferences and risk-taking behavior, often leading to suboptimal investment outcomes. The study contributes to the growing body of behavioural finance literature by providing insights into the psychological patterns of Indian retail investors and highlights the importance of financial literacy and behavioural training to promote rational investment decisions..