In response to the growing interest in multigenerational effects, we investigate whether grandparents’ education affects grandchildren’s transitions to academic high school and university in Taiwan. Drawing on social capital literature, we consider potential heterogeneity of the grandparent effect by parents’ characteristics and propose that grandparents’ education yields differential effects depending on parents’ education. Our results show tenuous effects of grandmother’s and grandfather’s years of schooling, net of parents’ education. However, the positive interaction effects between grandparents’ and parents’ years of schooling indicate that grandparents’ additional years of schooling are more beneficial to students with more educated parents than for students with less educated parents. The diverging gap in the likelihood of attending academic high school or university between students with parents in higher and lower ends of the educational hierarchy, along with increased levels of grandparents’ education, supports our hypothesis that grandparents’ education augments educational inequality by parents’ education.