The current study evaluated the relative roles of conceptual knowledge and executive control on the development of categorical flexibility, the ability to switch between simultaneously available but conflicting categorical representations of an object. Experiment 1 assessed conceptual knowledge and executive control together; Experiment 2 differentiated conceptual knowledge from costly executive processes. In Experiment 1, 3- to 5-year-olds were given a three-choice (taxonomic, thematic, and nonassociate) match-to-sample task and asked to match two associates. In Experiment 2, same-aged children were assessed on another match-to-sample task that reduced executive costs by presenting thematic and taxonomic associates on separate trials. By comparing performance across tasks, age-related changes resulting from conceptual knowledge and executive control indicated that conceptual knowledge of superordinate relations showed gains between 3 and 4 years, whereas gains in executive control were seen between 4 and 5 years, suggesting a décalage in the development of conceptual and executive processes underlying categorical flexibility.