Childhood maltreatment is thought to be associated with suicidality in patients with obsessive-compulsive disorder (OCD). Although the underlying mechanism of this relationship is not clear, cognitive emotion regulation strategies (CERSs) and the specific OC symptoms including unacceptable obsessional thoughts (UOTs) and responsibility for harm (RFH) may underlie this link. Accordingly, the study aimed to assess the effect of childhood maltreatment on suicidal ideation through UOTs, RFH and adaptive and maladaptive CERSs in OCD patients. Three hundred patients meeting a DSM-5 diagnosis of OCD were selected and completed the scales measuring childhood maltreatment, OCD, suicidality and depressive symptoms. After controlling for depressive symptoms and OCD severity, childhood maltreatment was shown to affect suicidal ideation directly. Also, the indirect effect of childhood maltreatment on suicidal ideation was mediated by adaptive CERSs, UOTs and RFH.The findings show that OCD patients with a history of childhood maltreatment, less use of adaptive CERSs and the experiences of UOTs and RFH should be carefully considered regarding suicidal risk.