Objectives This study is designed to compare the clinical characteristics of patients with early onset schizophrenia to those of adult onset schizophrenia patients in first episode. Methods Authors reviewed medical records of 16 early-onset schizophrenia patients and 22 adult-onset schizophrenia patients who had been admitted in the psychiatric ward and diagnosed as schizophrenia according to Diagnostic and Statistical Manual of Mental Disorders, fourth Edition (DSM-IV) at Eulji University Hospital during 2004-2008. Socio-demographic data and clinical characteristics such as duration between onset and active phase, number of significant positive and negative symptoms, positive and negative symptom scores of Positive and Negative Syndrome Scale (PANSS), Clinical Global Impression-Severity (CGI-S) scores, duration from onset to admission, duration of admission, and equivalent dose of antipsychotics were reviewed. These clinical characteristics of early-onset group were compared to those of adult-onset group. Correlation between age of onset and other clinical characteristics was also analyzed. Results Early-onset group showed more insidious onset pattern and had longer duration of hospitalization than adult-onset group. Early onset group also exhibited more negative symptoms, higher negative symptom scores, and higher CGI-S scores than adult-onset group after treatment. However, there were no significant differences in family history of psychosis, positive symptom frequency at discharge and equivalent dose of antipsychotics between two groups. Conclusions This study revealed that patients with early-onset schizophrenia exhibited more insidious onset, more negative symptoms, and more severe symptoms than those with adult-onset schizophrenia after treatment.