Police, ambulance, and mental health tri-response services are a relatively new model of responding to people experiencing mental health crisis in the community, though limited evidence exists examining their efficacy. Reducing unnecessary involuntary detentions and emergency department presentations is believed to be a benefit of this model. A systematic review was performed to review the evidence base around the relationship between the police, ambulance, mental health tri-response models in reducing involuntary detentions of people experiencing mental health crisis. We searched key health databases for clinical studies and grey literature as per a previously published protocol. Two researchers completed title and abstract screening and full text screening. Our search identified 239 citations. No studies or grey literature met the inclusion criteria. We report an empty review. It is recommended that further investigation of the tri-response mental health crisis model be undertaken to determine its effectiveness and value as a health and emergency service initiative.