Previous research has shown that female doctoral graduates earn less than male doctoral graduates; however, there has been little research on the determinants of this gender pay gap. This paper investigates the determinants of the gender pay gap among doctoral graduates in Germany. By relying on human capital theory, traditional gender roles and beliefs, and previous empirical findings, I examine gender differences in doctoral and occupational characteristics as potential determinants of the gender pay gap. I use data from a representative German panel study of the 2014 doctoral graduation cohort. Regression analyses on the logarithmic gross monthly earnings reveal that female graduates earn 30.4% less than male graduates five years after graduation. This gender pay gap is driven by a substantive wage premium for male doctoral graduates outside academia. Important determinants of the overall gender pay gap are doctoral subjects, professional experience after graduation, industries, management positions, and, above all, working hours. However, the considered determinants only partially explain the gender pay gap, as it remains substantial and statistically significant. The paper enhances the research on gender inequalities in post-doctoral careers and offers new insights into the determinants of the gender pay gap among doctoral graduates.