Over the past decades, Cloninger et al. have developed a biosocial model of personality based on four temperaments and three characteristics. This multidimensional psychobiological model of personality presents in the temperament and character inventory – revised (TCI-R) form. Temperament subscales are novelty seeking (NS), harm avoidance (HA), reward dependence (RD), and persistence (P), and character subscales are self-directedness (SD), cooperativeness (CO), and self-transcendence (ST). The study has been used in different disciplines of science, especially in psychology. Behavioral finance is one of these disciplines of science. TCI is frequently used, especially for investor biases. In this chapter, TCI is used to examine the relationship between investor biases and personality. The first three chapters are about personality. Personality, personality approaches, and personality measurement methods examined in these sections. In the fourth part, emotional biases in financial investment decisions searched. In the fifth part, literature studies showing the relationship between personality and financial decisions included. Finally, a field survey is conducted, and findings are revealed.