Abstract Background People experiencing a mental health crisis receive variable and poorer quality care than those experiencing a physical health crisis. Little is known about the epidemiology, subsequent care pathways of mental health and self-harm emergencies attended by ambulance services, and subsequent all-cause mortality, including deaths by suicide. This is the first national epidemiological analysis of the processes and outcomes of people attended by an ambulance due to a mental health or self-harm emergency. The study aimed to describe patient characteristics, volume, case-mix, outcomes and care pathways following ambulance attendance in this patient population. Methods A linked data study of Scottish ambulance service, emergency department, acute inpatient and death records for adults aged ≥16 for one full year following index ambulance attendance in 2011. Results The ambulance service attended 6802 mental health or self harm coded patients on 9014 occasions. This represents 11% of all calls attended that year. Various pathways resulted from these attendances. Most frequent were those that resulted in transportation to and discharge from the emergency department (n = 4566/9014; 51%). Some patients were left at home (n = 1003/9014 attendances, 11%). Others were admitted to hospital (n = 2043/9014, 23%). Within 12 months of initial attendance, 279 (4%) patients had died, 97 of these were recorded as suicide. Conclusions This unique study finds that ambulance service and emergency departments are missing opportunities to provide better care to this population and in potentially avoidable mortality, morbidity and service burden. Developing and testing interventions for this patient group in pre-hospital and emergency department settings could lead to reductions in suicide, patient distress, and service usage.