This study assessed 562 four-year-old children at the beginning and end of their prekindergarten (pre-k) year and followed them to the end of kindergarten. At each time point children were assessed on 6 measures of executive function (EF) and 5 subtests of the Woodcock–Johnson III academic achievement battery. Exploratory factor analyses yielded EF and achievement factor scores. We examined the longitudinal bidirectional associations between these domains as well as the bidirectional associations among the separate content areas and the EF factor. In the pre-k year, strong bidirectional associations were found for EF skills and mathematics and oral comprehension skills but not for literacy skills. After controlling for pre-k gains in both EF and achievement, EF skills continued to be strong predictors of gains in mathematics in kindergarten and a more moderate predictor of kindergarten language gains. These results provide important information on the interrelationship of the developmental domains of EF and achievement as well as support for efforts to determine effective pre-k activities and/or curricula that can improve children’s EF skills. They also suggest that mathematics activities may be a possible avenue for improving EF skills in young children.