Encouraging women to pursue degrees and employment in STEM (science, technology, engineering, and mathematics) fields is a key component of government and industry efforts to reduce gender inequality. Yet women’s representation in computer science occupations has declined since the 1980s. Research has found that family factors – marriage and parenthood – are important drivers of gender imbalance in STEM careers (Cech and Blair-Loy 2019). We use data from the 2009-2018 American Community Survey to examine factors contributing to gender differences in earnings among those working full-time in computer science. The results show a persistent gender wage gap in computer science, even after controlling for human capital and family attributes. Our findings challenge explanations that family factors account for gender disparities in earnings in computer science. The wage gap emerges well before the prime family formation years. We find no evidence of a marriage penalty for women working in computer science, though men earn a considerable marriage premium. The motherhood penalty is limited to women with infants; mothers of older children earn a wage premium, though it is significantly smaller than the fatherhood bonus. Differential returns to attributes – often attributed to discrimination – account for three-quarters of the gender wage gap.