Party identification has a crucial influence on individual political attitudes and behavior. Although many past studies have identified the factors affecting individual party identification, little scholarly attention has been paid to the relationships between dispositional factors and party identification. Therefore, this study aims to examine how personality traits influence individual partisanship, that is, whether the traits of extraversion, agreeableness, conscientiousness, emotional stability, and openness to experience would make individuals become partisans or independents. By using two original survey datasets, this study finds that the Big Five personality traits have no direct effects on Taiwanese people’s partisanship, but they could exert indirect effects on partisanship through political interest and strength of individual position on the independence-unification issue. Specifically, agreeableness and conscientiousness could respectively have a negative or positive indirect effect on partisanship via political interest. Besides, agreeableness and openness to experience could respectively have a negative or positive indirect effect on partisanship via individual position on the independence-unification issue. Consequently, although this study reveals no direct relationships between personality traits and partisanship, it does not necessarily mean that personality traits have nothing to do with partisanship. In fact, personality traits could indirectly influence Taiwanese people’s partisanship through the mediation of political attitudes. To sum up, this study confirms that dispositional factors could have a certain influence on Taiwanese people’s partisanship and provides a new theoretical perspective to explain Taiwanese people’s party identification. However, due to data limitations, this study only provides an exploratory analysis, and calls for future research to identify more complete relationships between personality traits and Taiwanese people’s party identification.