The decision for psychiatric hospitalization after deliberate self-poisoning (DSP) is not well understood. This study, a longitudinal cohort study of 3,148 consecutive DSP patients found 920 (29.2%) subjects were referred for psychiatric hospitalization, 576 (18.3%) on involuntary basis. A logistic regression analysis showed increased risk for: age 25 or older, homelessness, unemployment, previous self-harm, psychiatric inpatient treatment within 12 months, earlier psychiatric inpatient treatment, suicidal ideation or plan, mood or psychotic disorders, and lower clinician experience; and lower risk for being married/defacto, and after hours presentation. Recommendation for psychiatric hospitalization was based on complex decision making. These findings have implications for clinical practice guidelines, service costs, and service organization.