In the present work, we investigate the hypothesis that failures of task-related executive control that occur during episodes of mind wandering are associated with an increase in extraneous movements (fidgeting). In 2 studies, we assessed mind wandering using thought probes while participants performed the metronome response task (MRT), which required them to synchronize button presses with tones. Participants performed this task while sitting on a Wii Balance Board providing us with an index of fidgeting. Results of Study 1 demonstrate that relative to on-task periods, mind wandering is indeed accompanied by increases in fidgeting, as well as increased response variability in the MRT. In Study 2, we observed that only deep mind wandering was associated with increases in fidgeting, whereas task-related response variability increased even during mild mind wandering. We interpret these findings in the context of current theories of mind wandering and suggest that (a) mind wandering is associated with costs not only to primary-task performance but also to secondary-task goals (e.g., controlling extraneous movements) and (b) these costs may depend on the degree to which task-related executive control processes are disengaged during mind wandering (i.e., depth of mind wandering).