Abstarct: The present study aimed to investigate the mediating role of behavioral biases in the relationship between financial literacy and investment performance in Diyala, Iraq. The statistical population consisted of individual investors in the investment market of Diyala, Iraq. Using a convenience sampling method, a sample of 384 participants was selected baxsed on Cochran’s formula. In terms of purpose, this study was applied research and, in terms of methodology, it was descxriptive and survey-baxsed. The validity of the questionnaires was confirmed by the supervisor and further supported through the assessment of convergent and discriminant validity. The reliability of the questionnaires was evaluated using Cronbach’s alpha coefficients, all of which were above 0.70 and therefore considered acceptable. The findings indicated that financial literacy had a significant effect on investment performance through the mediating role of overconfidence bias. Furthermore, representativeness bias mediated the effect of financial literacy on investment performance. Herding bias also played a mediating role in the relationship between financial literacy and investment performance. In addition, financial literacy affected investment performance through the mediating role of anchoring bias.