Abstract. Public service motivation (PSM) has become a popular topic discussed in various studies concerning the public sector. However, there is still limited literature discussing PSM, transformational leadership, and affective commitment simultaneously. Therefore, this study aims to examine the role of transformational leadership on affective commitment in the public sector by considering PSM as a mediating variable in the Indonesian context. This study applies a quantitative approach based on data collected from 172 Customs and Excise employee respondents. Primary data was obtained through a purposive sampling method and analyzed using a structural equation model (SEM). The results indicate a positive and significant influence of transformational leadership on PSM, PSM on affective commitment, and transformational leadership on affective commitment. However, the findings show that PSM does not mediate the effect of transformational leadership on affective commitment. The study also addresses some theoretical contributions and managerial implications concerning these topics. Keywords: Transformational leadership, affective commitment, public sector, public service motivation, mediating variable