Objective: To improve awareness of the differential diagnosis between schizophrenia and dissociative identity disorder (DID) and to reduce clinical misdiagnosis. Methods: The study reported the data of one adolescent patient who presented with prominent and complex “multiple personality”-like manifestations and was definitively diagnosed with schizophrenia after consultation with Professor Du Yasong at the Shanghai Mental Health Center. The clinical characteristics and key points of differential diagnosis were analyzed in conjunction with a literature review. Results: The patient was a 15-year-old male who initially presented with depressed mood and suicidal ideation. During the course of illness, three alternating independent “personalities” emerged (“Luomu,” “Jiangyuling,” and “Luofeiyu”). He had previously been diagnosed with “multiple personality disorder” and “major depressive disorder” at other hospitals. Following detailed mental status examination and expert consultation, the patient was found to have clear auditory hallucinations of a commentary and commanding nature, visual hallucinations (seeing a man following and frightening him), grandiose delusions (believing he could control other personalities within his body), affective incongruity, and severe impairment of social functioning. His “personality switching” was accompanied by partial disturbance of consciousness and memory loss, but he lacked a typical history of severe childhood trauma. The diagnosis was revised to schizophrenia. After treatment with risperidone, the psychotic symptoms improved significantly, the “personality switching” phenomenon gradually disappeared, and social functioning progressively recovered. Conclusion: For patients whose primary clinical presentation is “multiple personality”-like manifestations, the possibility of schizophrenia should be considered. Meticulous longitudinal history-taking, identification of core psychotic symptoms, and assessment of the state of consciousness and memory loss during “personality switching” are key to differential diagnosis.