Previous studies have reported childhood emotional maltreatment (CEM) to be associated with specific obsessive–compulsive (OC) symptoms, but maladaptive coping, which may be the underlying mechanism in this relationship, has not been evaluated yet. Thus, the present study aimed to examine the effects of CEM on the OC symptoms of responsibility for harm and unacceptable thoughts, as well as obsessive–compulsive disorder (OCD) severity, through maladaptive coping, including cognitive avoidance, experiential avoidance and emotional suppression in OCD patients (n = 360). The results showed that CEM had direct effects, as well as indirect effects via cognitive and experiential avoidance and emotional suppression, on responsibility for harm and unacceptable thoughts. In addition, the indirect effect of CEM on OCD severity was significantly mediated by the roles of cognitive avoidance and experiential avoidance. The present study adds new literature to evidence indicating the role of early childhood events in developing and maintaining OCD in which adverse maladaptive coping related to unpleasant childhood abuse plays an important role in OCD. More precisely, OCD patients who experience a history of CEM may further use maladaptive coping to cope with their distress and subsequently experience responsibility for harm, unacceptable thoughts and severe OCD.