Overgeneralization (i.e., the transfer of fear to stimuli not related to an aversive event) is part of alterations in associative fear learning in mental disorders. In the present experimental study, we investigated whether this holds true for post‐traumatic stress disorder (PTSD) related to childhood abuse. We expected that fear generalization under experimental conditions reflects generalization of aversive stimuli to different social domains in real life. Sixty‐four women with PTSD after childhood abuse and 30 healthy participants (HC) underwent a differential fear conditioning and generalization paradigm. Online risk ratings, reaction time, and fear‐potentiated startle served as dependent variables. Based on the subjectively assessed generalization of triggered intrusions across different domains of life, PTSD participants were split into two groups reporting low (low‐GEN) and high (high‐GEN) generalization. PTSD patients reported a higher expectation of an aversive event. During fear conditioning, they assessed the risk of danger related to a safety cue slower and showed a blunted fear‐potentiated startle toward the danger cue. During generalization testing, reaction time increased in the high‐GEN patients and decreased in the HC group with increasing similarity of a stimulus with the conditioned safety cue. Alterations of fear learning in PTSD suggest impaired defensive responses in case of a high threat probability. Moreover, our findings bridge the gap between the generalization of aversive cues during everyday life and laboratory‐based experimental parameters: impairments in the processing of cues signaling safety generalize particularly in those patients who report a spreading of PTSD symptoms across different domains of everyday life. Up to 75% of individuals who experienced physical and sexual abuse during childhood develop a post‐traumatic stress disorder (PTSD). The present experimental study contributes to the understanding of this disorder by revealing a complex picture of impairments in cognitive and emotional fear learning. A blunted fear‐potentiated startle revealed impaired defensive responses linked to the intensity and frequency of avoidance symptoms. Moreover, this is the first study that links overgeneralization of fear under experimental conditions to overgeneralization of aversive stimuli to different social domains in PTSD patients' real life.