BACKGROUND: Suicidality alone is insensitive to suicide risk among emergency department (ED) patients. OBJECTIVE: We describe the performance of adding an objective assessment of agitation to a suicide screening instrument for predicting suicide and self-harm after an ED encounter. METHODS: We tested the performance of a novel screener combining the presence of suicidality or agitation for predicting suicide within 90 days or a repeat ED visit for self-harm within 30 days using retrospective data from all patients seen in an urban safety net ED over 27 months. Patients were assessed for suicidality using the Columbia-Suicide Severity Rating Scale-Clinical Practice Screener and for agitation using either the Behavioral Activity Rating Scale or Richmond Agitation Sedation Scale. We hypothesized that a screener based on the presence of either suicidality or agitation would be more sensitive to suicide risk than the Columbia-Suicide Severity Rating Scale-Clinical Practice Screener alone. The screener's performance is described, and multivariable regression evaluates the correlations between screening and outcomes. RESULTS: The sample comprised 16,467 patients seen in the ED who had available suicide screening and agitation data. Thirteen patients (0.08%) died by suicide within 90 days after ED discharge. The sensitivity and specificity of the screener combining suicidality and agitation for predicting suicide was 0.69 (95% confidence interval, 0.44-0.94) and 0.74 (0.44-0.94), respectively. The sensitivity and specificity for agitation combined with positive suicide screening for self-harm within 30 days were 0.95 (0.89-1.00) and 0.73 (0.73-0.74). For both outcomes, augmenting the Columbia-Suicide Severity Rating Scale-Clinical Practice Screener with a measure of agitation improved both sensitivity and overall performance compared to historical performance of the Columbia-Suicide Severity Rating Scale-Clinical Practice Screener alone. CONCLUSIONS: Combining a brief objective measure of agitation with a common suicide screening instrument improved sensitivity and predictive performance for suicide and self-harm risk after ED discharge. These findings speak to the importance of assessing agitation not only for imminent safety risk during the patient encounter but also for reducing the likelihood of future adverse events. This work can improve the detection and management of suicide risk in emergency settings.