Obsessive-compulsive disorder (OCD) has been associated with altered performance monitoring reflected in enhanced amplitudes of the error-related negativity (ERN) in the event-related potential. However, this is not specific to OCD, as overactive error processing has also been associated with anxiety. Although similar neural mechanisms have been proposed for error and feedback processing, it remains unclear whether the processing of errors as indexed by external feedback, reflected in the feedback-related negativity (FRN), is altered in OCD. Likewise, it is currently unknown whether performance monitoring in OCD differs between learning from self-performed and observed outcomes. The present study compared OCD patients with healthy controls (HCs) and patients with social anxiety disorder (SAD) in an active and observational variant of a probabilistic feedback learning task while EEG was recorded. Compared to HCs, OCD patients showed impaired task performance in both active and observational learning, while choice behavior in OCD patients was generally more indecisive. This was accompanied by generally more positive amplitudes of the FRN, with enhanced valence coding for active compared to observational learning, driven by more positive FRN amplitudes for wins, though no differences emerged for losses. Conversely, amplitudes of the ERN did not differ between groups. Overall, these results suggest deficient reward—rather than punishment—processing in OCD. Similar performance monitoring alterations in OCD and SAD imply reliance on shared, disorder-general mechanisms. Possible candidates for these mechanisms, such as intolerance of uncertainty or pessimism, are discussed.