Single studies suggest that the effectiveness of certain instructional activities depends on teachers' judgment accuracy. However, sufficient empirical data is still lacking. In this longitudinal study (N = 75 teachers and 1,865 students), we assessed if the effectiveness of teacher feedback was moderated by judgment accuracy in a standardized reading program. For the purpose of a discriminant validation, moderating effects of teachers' judgment accuracy on their classroom management skills were examined. As expected, multilevel analyses revealed larger reading comprehension gains when teachers provided students with a high number of feedbacks and simultaneously demonstrated high judgment accuracy. Neither interactions nor main effects were found for classroom management skills on reading comprehension. Moreover, no significant interactions with judgment accuracy but main effects were found for both feedback and classroom management skills concerning reading strategy knowledge gains. The implications of the results are discussed.