Objective: Constipation is thought to be both common and overlooked in patients with schizophrenia, with no empirical data about its prevalence in the schizophrenic population in Taiwan. In the current study, we intended to investigate prevalence and risk factors of constipation during routine treatment of patients with schizophrenia. Method: We did a retrospective study of inpatients treated with antipsychotic medications in Kaohsiung Kai Syuan Municipal Psychiatric Hospital between January 2008 and December 2013. Totally, 3,107 inpatients diagnosed as schizophrenic were included in this study. Results: The prevalence of constipation was 28.10%. Female gender (odds ratio = 2.12, 95% confidence interval = 1.76 - 2.55, p ＜ 0.01), older age (OR = 1.02, 95% CI = 1.76 - 2.55, p ＜ 0.01), greater symptom severity (OR = 1.03, 95% CI = 1.01 - 1.04, p ＜ 0.01), and comorbid medical diseases (OR = 1.99, 95% CI = 1.65 - 2.40, p ＜ 0.01) were found to be all significantly positive factors related to the constipation. We also found that the use of second-generation antipsychotic drugs (OR = 1.75, 95% CI =1.24- 2.48, p ＜ 0.01), and the use of SGAs combined with first-generation antipsychotic drugs (OR = 3.78, 95% CI = 2.70 - 5.28, p ＜ 0.01) were significantly more likely to cause constipation than the use of FGAs alone. Conclusion: Those findings suggest that clinicians need greater vigilance and active evaluation of constipation in patients with schizophrenia, to ensure appropriate clinical management and to prevent associated complications.