In this study, the impact of behavioural finance on investment decision-making using a selected investment banks was investigated. A total of 200 questionnaire items were administered to the respondents of the four surveyed investment banks including Afrinvest West Africa Limited, Meristem Securities, Vetiva Capital and ARM Nigeria Limited, out of which 180 questionnaire items representing 90 per cent were retrieved. The data were analyzed using tables, percentages, correlation and multiple regression analysis. The overall empirical results provided evidence of a positive impact between behavioural finance and investment decision, supporting previous research and contributing to generalization. The other findings of the research are thus: there is a significant relationship between heuristics and individual investment decision; there is a significant relationship between prospect theory and individual investment decision; and lastly there is a strong and negative relationship between heuristics and investment decision. Similarly, the relationship between prospect theory and investment decision is negative and strong. Against the backdrop of the aforementioned findings and conclusion, the following recommendations are proposed to both the institutional and individual investors: investors should be enlightened on the fact that there are many behavioural factors which can affect their investment decision-making process and they should be made aware of these factors including heuristics and prospect theory.