Introduction: Prehospital transport of patients to an alternative destination (diversion) has been proposed as part of a solution to overcrowding in emergency departments (ED). We evaluated compliance and safety of an EMS protocol allowing paramedics to transport medically stable patients with psychiatric issues directly to an alternate facility [Crisis Intervention (CI)], bypassing the ED. Patients were eligible for diversion if they were ≥18 years old, classified as CTAS III-IV, scored <4 on the Prehospital Early Warning (PHEW) score, and did not have any vital sign parameters in a danger zone (as per PHEW score criteria). Methods: A retrospective analysis was conducted on patients presenting to Sudbury EMS with behavioural or psychiatric issues. Data was abstracted from EMS reports, hospital medical records, and discharge forms from CI. Protocol compliance was measured using missed protocol opportunities (patients eligible for diversion but taken directly to the ED) and protocol noncompliance rates; protocol safety was measured using protocol failure (presentation to ED within 48 hours of appropriate diversion) and patient morbidity rates (hospital admission within 48 hours of diversion). Data was analysed qualitatively and quantitatively using proportions. Results: EMS responded to 695 calls with psychiatric complaints. Of the 650 taken directly to the ED, 18 met diversion criteria; these were missed protocol opportunities (3%). 45 patients were diverted. There was protocol noncompliance in 36 cases (80%), but 34 were due to incomplete recording of vital signs. There were direct protocol violations in only 2 cases (4%). There was protocol failure in 3 cases (33%), and patient morbidity in 8 cases (18%). No patients died within 48 hours of diversion. Conclusion: EMS providers were highly compliant with the protocol when transporting patients directly to the ED. There were high levels of protocol non-compliance in diverting patients to CI, though this is largely attributed to incomplete recording of vital signs; direct protocol violations were low. The protocol provides moderate levels of safety in diverted patients. Broader implementation of a diversion protocol could reduce the volume of mental health patients seen in the ED, and improve quality of care received by this patient population.