OGBEIDE, SUNDAY OSEIWEHUGBOGBO, SUNDAY NOSA2023-10-042023-10-042022-122682-6135http://repository.elizadeuniversity.edu.ng/jspui/handle/20.500.12398/1413This study investigated cognitive and emotional behavioural finance biases and investors’ investment decision making in the Nigerian capital market. The cognitive behavioural finance biases examined were overconfidence bias and self-attribution bias; while the emotional behavioural finance bias were illusion of control bias and regret bias. The study used the survey-descriptive research design while four-point scale likert-type questionnaire was employed as the research instrument to elicit responses from one hundred respondents selected using the simple random sampling method. The data was analyzedusing the ordinary least squares (OLS) multiple regression method. Findings from the research showed a positive and significant effect of overconfidence bias, self-attribution bias, illusion of control bias and regret bias on the investors’ investment decision making in the Nigerian bourse. Illusion of control demonstrated little effect on investment decision making compared to other biases examined. The study concluded that both cognitive and emotional behavioural finance biases are key drivers of investors’ investment decision making in the Nigerian stock market. The study therefore recommends that investors should frequently form a proper pattern of judging and observing the behaviour of others while decisions are being made.enOverconfidence biasSelf-attribution biasIllusion of Control biasRegret biasInvestors’ Decision MakingArticle