Patients with somatization disorder (SD) endorse high rates of psychiatric symptoms. However, prior studies have not addressed whether these endorsed symptoms reflect underlying psychiatric illness or whether they represent symptom overendorsement mirroring somatic complaints in patients with SD. Thirty-two female outpatients with SD and 101 with other psychiatric disorders completed a checklist of current and lifetime psychiatric symptoms. These findings were analyzed with respect to the diagnoses given by their treating psychiatrists. Patients with SD displayed significantly more current and lifetime psychiatric symptoms than did patients without either SD or cluster B personality disorder. Patients with SD endorsed a large number of psychotic, manic, depressive, and anxiety symptoms; however, they endorsed few alcohol use disorder symptoms. Psychotic and manic symptoms endorsed by patients with SD did not reflect their clinical diagnoses: only two patients with SD carried an additional clinician diagnosis of either schizophrenia or bipolar disorder, despite high rates of endorsed symptoms by the group. Patients with cluster B personality disorders but without SD showed a symptom profile similar to that of patients with SD. Psychiatric outpatients with SD endorse many more psychiatric symptoms than do other psychiatric patients. Patients with SD in the psychiatric treatment setting may mimic other psychiatric illnesses; therefore, SD should be considered in the differential diagnosis for a wide variety of psychiatric illness, including psychotic and mood disorders.