Parents' judgment of their children's cognitive ability is important for providing adequate learning environments. This study examined parents' judgment accuracy with 2346 children (M = 8.94 years; 48.3% girls) and their parents (1283 mothers, 426 fathers, and 637 parental pairs). The data were collected between September 2012 and February 2014 in Germany. Latent regression analyses were conducted for the overall sample and by grade (n[subscript Grade1&2] = 830; n[subscript Grade3&4] = 1516). Characteristics of the child (gender, birth order) and parents (gender, socioeconomic background) were investigated as moderators. Children's cognitive ability explained 34%/25%/37% (overall sample/Grade1&2/Grade3&4) of the variance in parental judgments. Judgments depended more on children's academic achievement than on cognitive ability. Parents judged their son's intelligence more accurately than their daughter's and first-born children more accurately than last-born children. Higher-educated parents showed higher judgment accuracy.