Accessible Summary: What is known on the subject: Police and ambulance staff are increasingly asked to help people experiencing mental health crises, but they often feel under‐prepared.The single frontline service approach is time‐intensive and risks a coercive pathway to care.The emergency department is the default location for transfers by police or ambulance involving a person involved in a mental health crisis, despite being viewed as suboptimal. What the paper adds to existing knowledge: Police and ambulance staff struggled keeping up with the mental health demand, reporting inadequate mental health training, little enjoyment and negative experiences when trying to access help from other services.Most mental health staff had adequate mental health training and enjoyed their work, but many experienced difficulties getting help from other services.Police and ambulance staff found it hard to work with mental health services. What are the implications for practice: The combination of limited training, poor interagency referral processes, and difficulties accessing support from mental health services means that when police and ambulance services attend mental health crises alone, distress may be heightened and prolonged. Enhanced mental health training for first responders and more streamlined referral processes may improve process and outcomes.Mental health nurses have key skills that could be utilized in assisting police and ambulance staff who attend 911 emergency mental health calls.New models such as co‐response teams, whereby police, mental health clinicians and ambulance staff respond conjointly should be trialled and evaluated. Introduction: First responders are increasingly called to assist people experiencing mental health crises but little research exists canvassing multi‐agency perspectives of such work. Aim/Question: To understand the views of police officers, ambulance and mental health staff attending mental health or suicide‐related crises in Aotearoa New Zealand and to discover how they experience current models of cross‐agency collaboration. Methods: A descriptive cross‐sectional survey involving mixed methods. Quantitative data were analysed using descriptive statistics and free text by content analysis. Results: Participants included 57 police officers, 29 paramedics and 33 mental health professionals. Mental health staff felt adequately trained, but only 36% described good processes for accessing inter‐agency support. Police and ambulance staff felt undertrained and unprepared. Accessing mental health expertise was considered difficult by 89% of police and 62% of ambulance staff. Discussion: Frontline services struggle managing mental health‐related 911 emergencies. Current models are not working well. Miscommunication, dissatisfaction and distrust exist between police, ambulance and mental health services. Conclusion: The single‐agency frontline response may be detrimental to service users in crisis and under‐utilizes the skills of mental health staff. New ways of inter‐agency cooperation are required, such as co‐located police, ambulance and mental health nurses responding in partnership. [ABSTRACT FROM AUTHOR]