Obsessive- compulsive disorder (OCD) patients show hyperactive performance monitoring when monitoring their own actions. Hyperactive performance monitoring is related to OCD symptomatology, like the unflexibility of compulsive behaviors, and was suggested as a potential endophenotype for the disorder. However, thus far the functioning of the performance monitoring system in OCD remains unclear in processes where performance is not monitored in one's own actions internally, but through external feedback during learning. The present study investigated whether electrocortical indicators of feedback processing are hyperactive, and whether feedback-guided learning is compromised in OCD. A modified deterministic four-choice object reversal learning task was used that required recurrent feedback-based behavioral adjustment in response to changing reward contingencies. Electrophysiological correlates of feedback processing (i.e. feedback-related negativity [FRN] and P300) were measured in 25 OCD patients and 25 matched healthy comparison subjects. Deficits in behavioral adjustment were found in terms of higher error rates of OCD patients in response to negative feedback. Whereas the FRN was unchanged for reversal negative feedback, it was reduced for negative feedback that indicated that a newly selected stimulus was still incorrect. The observed FRN reduction suggests attenuated monitoring of feedback during the learning process in OCD potentially contributing to a deficit in adaptive behavior reflected in obsessive thoughts and actions. The reduction of FRN amplitudes contrasts with overactive performance monitoring of self-generated errors. Nevertheless, the findings contribute to the theoretical framework of performance monitoring, suggesting a dissociation of processing systems for actions and feedback with specific alterations of these two systems in OCD.