•Finger movements (key-pressing and key-releasing) with relatively faster reaction times can elicit stronger midfrontal delta-theta (1–7 Hz) neural oscillatory activity and stronger contralateral delta-theta functional connectivity compared to movements with slower reaction times, which reflects differences in movement difficulty, as simpler movements typically entail better motor control.•Movement difficulty modulates the impact of mind wandering on motor control, as evidenced by mind wandering only attenuating the midfrontal delta-theta activity (1–7 Hz) and contralateral delta-theta functional connectivity of relatively simple movements while not affecting more relatively difficult movements.•Mind wandering results in larger alpha ERD (8–13 Hz) during movement execution compared to on-task states regardless of movement difficulty, which may reflect the inefficiency of generating movement. It has been found that mind wandering can impair motor control. However, it remains unclear whether the impact of mind wandering on motor control is modulated by movement difficulty and its associated neural mechanisms. To address this issue, we manipulated movement difficulty using handedness and finger dexterity separately in two signal-response tasks with identical experiment designs, in which right-handed participants performed key-pressing and key-releasing movements with the specified fingers, and they had to intermittently report whether their attention was “On task” or “Off task.” Key-releasing with the right index finger (RI) had a faster reaction time and stronger contralateral delta-theta (1–7 Hz) functional connectivity than with the left index (LI) in Experiment 1, and mind wandering only reduced the contralateral delta-theta functional connectivity and midfrontal delta-theta activity for key-releasing with RI. Key-pressing with right index and middle fingers (RIR) had a faster reaction time and stronger midfrontal delta-theta activity than with right index and ring fingers (RIR) in Experiment 2, and mind wandering only reduced the midfrontal delta-theta activity for key-pressing with RIM. Theta oscillations are vital in motor control. These findings suggest that mind wandering only impairs the motor control of relatively simple movements without affecting the difficult ones. It supports the notion that mind wandering competes for executive resources with the primary task. Moreover, the quantity of executive resources recruited for a task and how these resources are allocated is contingent upon the task difficulty, which may determine whether mind wandering would interfere with motor control.