BACKGROUND Current neurobiological models of obsessive-compulsive disorder (OCD) propose a dysfunction of cortico-striato-thalamo-cortical circuits that leads to enhanced activity in frontal and striatal brain regions. In accordance with that, OCD patients show alterations in learning and flexible adaptation to changing task requirements. The purpose of this study was to examine feedback-based learning and to investigate whether learning from positive and negative feedback is differentially altered in OCD. METHODS In this study, 18 OCD patients and 18 healthy comparison subjects conducted a probabilistic selection task. The task consisted of an acquisition and a test phase and allowed disentangling the extent of learning based on positive and negative feedback. RESULTS Groups did not differ during probabilistic feedback learning in the acquisition phase. In the test phase, OCD patients showed a negative learning bias in contrast to comparison subjects who showed a positive learning bias. Patients were better at avoiding stimuli that were initially associated with negative outcomes than at approaching stimuli that were associated with positive feedbacks. This interaction was also found for reaction times in that patients were faster in avoiding negative and slower in approaching positive stimuli. CONCLUSIONS Enhanced avoidance learning was found in OCD patients that points to exaggerated anticipation and avoidance of aversive outcomes. Further studies are required to investigate whether neurobiological mechanisms, such as dopaminergic signaling or outcome processing, in the orbitofrontal cortex relate to enhanced negative learning in OCD.