This research examined parents' involvement in children's math homework and activities. During 2017 to 2019, American parents (N = 483; 80% mothers; 67% white) of young elementary school children (M[subscript age] = 7.47 years; 50% girls) reported on their math helping self-efficacy; they also reported on their involvement in children's math homework and activities daily for 12 days. At this time and a year later, children's math motivation and achievement were assessed. Parents' involvement in homework (vs. activities) was more affectively negative (d = 0.34), particularly among parents low in self-efficacy (d = 0.23). The more affectively negative parents' involvement, particularly in homework, the poorer children's later math motivation and achievement ([beta]s = -0.09 to 0.20).