Objectives This study examined the factors associated with suicidal behavior in psychiatric inpatients. Methods The medical records of 208 psychiatric inpatients were reviewed retrospectively. The factors related to suicide attempts and ideation at the time of admission, and during outpatient follow-up, were investigated. Results In total, 120 patients (57.7%) with a history of at least one suicide attempt, and 163 patients (78.4%) who reported active suicide ideation (e.g., a suicide plan or intention to commit suicide) at the time of admission were reviewed. Being unmarried or divorced, substance abuse, impulsivity, and a poor social support system were associated with a history of suicide attempts. The suicidal ideation group had significantly higher rates of coexisting depression, severe depressive symptoms, hopelessness, and impulsivity, as well as a lower incidence of moral objection to suicide and high religiosity. In total, 15 out of 193 patients (7.8%) who were followed-up at outpatient clinics attempted suicide after discharge. Patients who attempted suicide or reported suicidal ideation at the outpatient clinic after discharge were significantly more likely to have a history of previous suicide attempts, or have had active suicide ideation at the time of admission. Good social support and high responsibility to family were inversely associated with suicidal ideation as an outpatient. Conclusion A history of suicide attempts and ideation at the time of hospital admission were the risk factors for future outpatient suicidal behavior. Further study is warranted to develop a checklist and assessment measures of the various risk and protective factors associated with suicidal behavior.