This study examined whether parental involvement in children's science schoolwork (i.e., discussions about science, homework helping and encouragement of science interest) varies for boys and girls, and how these behaviors relate to children's science achievement beliefs (i.e., ability perceptions and task-value) at the end of a school year. We analyzed these links both for fathers and mothers and examined whether child gender moderates how parental behaviors relate to children's beliefs over time. Data were gathered over a span of a school year from 114 middle-school students (50% girls, 81% European American) and their parents (mothers: n = 103, fathers: n = 90). We found support for the moderating effect of gender. Specifically, the findings indicated that only parents' encouragement of science interest varied by child gender; mothers' encouragement positively predicted girls' self-assessments of science ability at the end of the year, but was a negative estimator of boys' self-assessments. Additionally, mothers' discussions about science showed similar findings with respect to girls' and boys' utility beliefs about science.