The study objective was to determine the accuracy of initial triage assessment (ITA) in directing behavioral emergency patients to appropriate medical or psychiatric care, and to identify variables that enhance triage accuracy. A cohort study of 436 adult patients with 1 of 10 behavioral-related complaints was conducted. ITA compared with the final ED diagnosis, both of which were classified as either “medical” or “psychiatric.” Patient triage characteristics correlated with the final ED diagnosis using logistic regression. Sensitivity of ITA for predicting a medical final ED diagnosis was 70% (95% CI 60.1, 78.5) and specificity 85% (95% CI 80.6, 88.7). ITA agreed with final ED diagnosis in 344 (81.3%) and these patients had a significantly shorter ED length of stay (4.50 v 5.90 hours, p = 0.03). Dementia, past psychiatric history, family history of psychiatric illness, and ITA were significant predictors of final ED diagnosis. ITA is a fair predictor of the final ED diagnosis, but could be enhanced by screening for dementia and past psychiatric history. Improved triage accuracy could reduce length of stay for such patients.