The co-occurrence of epilepsy and psychiatric disorders is long known. The scope of this systematic review was to describe the prevalence of specific interictal psychiatric disorders in patients with epilepsy and to assess possible associations between psychiatric disorders and other sociodemographic or clinical characteristics of epilepsy patients. MEDLINE and ScienceDirect were searched for original articles published between January 2015 and February 2021 describing studies that involved epilepsy patients with psychiatric comorbidities. We identified 13 studies with heterogenous methodology and reporting. Prevalence of any psychiatric disorder observed was up to 51% in idiopathic generalized epilepsy (IGE), up to 43.1% in temporal lobe epilepsy (TLE) and up to 43.3% in a general population of patients with epilepsy. The most frequent psychiatric comorbidities associated with epilepsy included mood/affective disorders (up to 40% for lifetime occurrence and up to 23% for current occurrence), anxiety disorders (up to 30.8% for lifetime occurrence and up to 15.6% for current occurrence), personality disorders [up to 11% in juvenile myoclonic epilepsy (JME)] and psychotic disorders (up to 4% of epilepsy patients). In focal epilepsy, depressive disorders might be associated with specific brain imaging findings and with cognitive impairment. Anxiety disorders are associated with a higher frequency of generalized tonico-clonic seizure (GTCS) and with worse social functioning. Psychotic disorders were found to be associated with longer duration of epilepsy. Childhood maltreatment experiences were found to be a powerful predictor for the occurrence of psychiatric comorbidities in epilepsy patients, while data regarding association of other epilepsy characteristics with the presence of psychiatric disorders is conflicting.