Musician’s dystonia (MD) is a task-specific movement disorder characterized by a loss of voluntary motor control in highly trained movements like piano playing. Its underlying pathophysiology is defined by deficient functioning of neural pathways at different levels of the central nervous system. However, a few studies have examined the brain responses associated with executive functions such as error monitoring inMD.We recorded the electroencephalogram (EEG) in professional pianists during the performance of memorized music sequences at fast tempi. Event-related potentials (ERPs) locked to pitch errors were investigated in MD and a control group. In MD patients, significantly larger error-related brain responses before and following errors were observed as compared with healthy pianists. Our results suggest that in MD, the generalized degraded neural activity at all levels of the central nervous system is manifested in specific neural correlates of the executive functions that monitor an overlearned sensorimotor performance.