Healthcare facilities in low-income and middle-income countries lack an objective measurement tool to assess emergency care capacity. The African Federation for Emergency Medicine developed the Emergency Care Assessment Tool (ECAT) to fulfil this function. The ECAT assesses the provision of key medical interventions (signal functions) that emergency units (EUs) should be able to perform to adequately treat six common, life-threatening conditions (sentinel conditions). We describe the piloting and refinement of the ECAT, to improve usability and context-appropriateness. We undertook iterative, multisite refinement of the ECAT. After pilot testing at a South African referral hospital, subsequent studies occurred at district, regional and central facilities across four countries representing the major regions of Africa: Cameroon, Uganda, Egypt and Botswana. At each site, the tool was administered to three participants: one senior physician, one senior nurse and one other clinical provider. Feedback informed refinements of the ECAT, and an updated tool was used in the next-studied country. Iteratively implementing refined versions of the tool in various contexts across Africa resulted in a final ECAT that uses signal functions, categorised by sentinel conditions and evaluated against discrete barriers to emergency care service delivery, to assess EUs. It also allowed for refinement of administration and data analysis processes. The ECAT has a total of 71 items. Advanced facilities are expected to perform all 71 signal functions, while intermediate facilities should be able to perform 53. The ECAT is the first tool to provide a standardised method for assessing facility-based emergency care in the African context. It identifies where in the maturation process a hospital or system is and what gaps exist in delivery of care, so that a comprehensive roadmap for development can be established. Although validity and feasibility testing have now occurred, reliability studies must be conducted prior to amplification across the region.