Abnormalities in hippocampal morphology are characteristic of schizophrenia and have also been reported in chronic cannabis users. There is a paucity of research investigating potential additive effects of cannabis use on brain pathology associated with schizophrenia. In this study, we performed hippocampal shape analysis in cannabis-using and non-using patients with schizophrenia, healthy cannabis users and healthy non-using controls. Hippocampal shape changes were observed in each group relative to controls, with the greatest degree of alterations (i.e., deflations across the hippocampus, and with an anterior predisposition), in cannabis-using schizophrenia patients. These alterations were associated with cannabis use patterns and psychotic symptoms.