n the contemporary financial environment, working professionals are increasingly required to make independent and informed investment decisions to ensure financial security, wealth creation, and long-term stability. However, the growing availability of financial products and digital investment platforms does not necessarily guarantee effective decision-making, particularly when financial literacy levels vary across individuals. In this context, the present study examines the impact of financial literacy on personal investment decisions among working professionals in Chennai. The study considers financial literacy as a multidimensional construct comprising financial knowledge, financial behaviour, financial attitude, and investment information awareness. It also incorporates investment confidence as a key influencing factor and behavioural biases as a negative behavioural element affecting investment decision quality. The study adopted a quantitative research design and collected primary data from 400 working professionals in Chennai using a structured questionnaire. The collected data were analysed using percentage analysis, descriptive statistics, reliability analysis, exploratory factor analysis, correlation, multiple regression, ANOVA, and chi-square analysis. The findings revealed that the respondents demonstrated moderately high levels of financial literacy and personal investment decision quality. The study concludes that financial literacy plays a significant and positive role in improving the investment decisions of working professionals, while behavioural biases weaken rational financial judgement. The findings highlight the importance of strengthening practical financial behaviour, investment confidence, and investor education among urban working populations. The study offers useful implications for academicians, financial institutions, employers, and policy makers interested in improving personal financial decision-making and investor capability