Although suicide is difficult to predict in the general population, emergency department (ED) patients presenting with suicide risk factors such as substance abuse or depression are a readily identifiable population at elevated risk for suicidal behavior. However, little is known about which factors have the strongest association with future suicide outcomes. This study aimed to determine the predictors associated with suicide outcomes documented during the 12 months following an ED visit where the patient screened positive for active suicidal ideation or behavior. Data were collected during the first two phases of the Emergency Department Safety Assessment and Follow-up Evaluation (ED-SAFE), a quasi-experimental suicide intervention study involving eight EDs across the U.S. Sites enrolled adults with active suicidal ideation or an attempt in the last week. Data collection included baseline interview; 6- and 12-month chart reviews; and 6-, 12-, 24-, 36-, and 52-week telephone follow-up assessments. The suicide composite outcome included reporting a preparatory act (eg, buying pills), interrupted or aborted attempt, a suicide attempt, or a suicide in the 12 months following the initial ED visit. Variables with a univariable association with suicide outcomes at P<.10 were included in the multivariable logistic regression model. In the final model, P<.05 was considered statistically significant. Among the 874 subjects (phase 1=497; phase 2=377), the median age was 37 years (interquartile range 27-47) with 56% female, 74% white, and 87% non-Hispanic. At baseline, 577 (66%) had suicidal ideation only and 297 (34%) a suicide attempt in the last month. Twelve-month outcomes were available for 782 (90%), who completed at least one of the 5 telephone follow-up assessments or had documentation of a suicide attempt or suicide completion during the 6- or 12-month chart review. In the one year after the initial ED visit, 430 (55%) reported a preparatory act, interrupted or aborted attempt, a suicide attempt, or had committed suicide. Subjects were more likely to have suicidal behavior within one year after the initial ED visit if they reported at the initial ED visit that they had a high school education or less (OR 1.63; 95% CI, 1.18-2.26; P=.003), had a primary care provider (OR 1.43; 95% CI, 1.01-2.00; P=.04), were unemployed (OR 1.64; 95% CI, 1.16-2.32; P=.006), had active suicidal ideation with a plan and intent to act (OR 10.2; 95% CI, 1.13-91.56; P=.04), had a severe health issue (eg, stroke, HIV) (OR 1.49; 95% CI, 1.06-2.10; P=.02), had a history of mental health problem(s) (OR 1.99; 95% CI, 1.14-3.47; P=.02), or a had a history of suicide attempt(s) (OR 1.60; 95% CI, 1.11-2.30; P=.01). The strongest predictors of reporting suicidal behavior within one year after the initial ED visit were related to patient characteristics (demographics and medical history) and past suicidal ideation and behavior. This suggests that in addition to psychiatric history, individual characteristics such as education level and employment as well as severe medical conditions should be considered when assessing suicide risk in an adult ED population. Understanding the factors that predict future suicide behaviors for this population will help guide the design and implementation of improved suicide-related interventions in the ED.