Objective The aim of this study was to investigate the predictor variables that could influence overlap syndrome in functional gastrointestinal disorders (FGID) among psychiatric patients. Methods Data collected from 170 outpatients visiting the psychiatric clinic at a university hospital. FGIDs were screened according to the Rome III questionnaire-Korean version. Demographic factors were investigated, and psychosocial factors were evaluated using the Hospital Anxiety Depression Scale, Patient Health Questionnaire-15, Childhood Trauma Questionnaire-Korean and the Short form health survey. Chi-squared test, Student’s t-test, one-way ANOVA, and Pearson’s correlation test were used as statistical analysis methods. Results There were no differences in the epidemiologic data between the two groups divided according to the FGID status. In those with FGID overlap syndrome, FD-NERD was most common (n=29), followed by IBS-NERD (n=20). Patients with overlap syndrome had the highest depressive, anxiety, and somatic symptoms. The overlap syndrome group had the lowest physical component summary and mental component summary. FGID symptom severity was significantly correlated with PCS and MCS in the overlap syndrome group. Conclusion Psychological factors are associated with the overlap syndrome of FGID. Acknowledging this common comorbidity may facilitate the recognition and treatment of patients with FGID.