Two studies investigated the parallel developmental progress in theory of mind and executive control, as exemplified by correlations between the Dimensional Change Card Sorting task (DCCS; Frye, Zelazo, & Palfai, 1995) and the false-belief task. Experiment 1 with sixty 3-year-old children confirmed earlier studies (e.g., Perner & Lang, 2002), suggesting that children's problem with the DCCS lies in the redescription of stimulus objects. Experiment 2 with forty-four 3- to 4-year-olds reinforced the correlational evidence for a developmental link by showing transfer of training: False-belief training improved DCCS performance, and DCCS training significantly increased children's performance on the false-belief task. Results are discussed in relation to 5 theories explaining the existing correlational evidence.