Schools outside of an English-speaking nation and delivering a curriculum in English have seen a rapid rise in numbers globally to over 12000, more than doubling in the past two decades. With this rise in international schools has come greater diversity, especially across Asia and in particular the Greater ASEAN region (GAR). There has been an increase in the number of schools recruiting teachers and leaders from their home countries or other continents. The majority of these are still Western expatriates. As international schools have an ever-growing footprint, it is understandable that many would face situations or incidents of a critical nature, such as student or staff accidental death. International school leaders (Principals / Directors) habitually rely on experience and knowledge to deal with incidents. My study defines critical incidents. It poses three questions to understand and support school leaders during these times. The first investigates the nature and challenge of critical incidents. The second examines the challenges of cultural leadership in such a culturally diverse landscape. Finally, the third considers the nature of school ownership and accreditation and the impact these have on school leaders when dealing with critical incidents. Whilst the body of knowledge for intercultural competence is growing, especially in an international school setting, there is scant literature on the nature of critical incidents occurring across intercultural settings. School leaders are often working in isolation and will benefit from understanding how cultural awareness or school ownership impact on the way situations are led and managed. School leaders already work across cultural boundaries in a range of international schools and need to deal with critical incidents in a culturally diverse environment. In an environment where local parents and owners are increasing, it is intended that the findings presented will support and help prepare international school leaders. The study used a mixed-method approach. A piloted survey of 14 international school leaders working in the GAR supported a final survey of 122 participants. The survey was followed by a smaller sample of in-depth semi-structured interviews of 17 school leaders across ten countries. The online interviews supported a case study approach to an understanding of incidents occurring within each of their schools. Interview data were collected and analysed using NVivo12 for the use of thematic analysis. Combined with the survey data, the thematic analysis gave an in-depth understanding of critical incidents, which was used to develop guidance for leaders of international schools. From the first research question, a classification of incidents was developed, which is broad, flexible, and based on a three-tiered model. The model is comprised of the where, who, and what elements that are commonly found in the schools across the region. With the addition of local knowledge for support agencies, this model will potentially assist international school leaders when dealing with a wide variety of critical incidents. The second of my research questions allowed for greater understanding of the cultural pressures faced by international school leaders. Cultural pressures came from the students, parents, ownership, and wider community. The need for leaders to have a cultural dexterity to navigate others' cultural tolerance, ignorance, arrogance, and empathy is identified and explored. Furthermore, the data showed that five categories of schools can be identified. Building upon Cambridge and Thompson's (2013) typology for three school categories, I have now added a further two, types D and E. Increasing the categories has allowed for a clearer understanding of how school ownership could impact on the management and leadership of critical incidents.