This paper reports the results of a study that sought to identify issues relating to the impact of increasing ethnocultural diversity in schools on principals’ decision-making. The research explored the perceptions of high (or secondary) school principals from three different sub-national jurisdictions in Australia, Canada, and New Zealand, each of which is receiving new citizens from a variety of different countries. The context of the research is provided by briefly describing the ethnocultural diversity of the three cities in which the research was conducted. Some of the relevant literature is then examined, followed by a discussion of the research methodology. The findings from the study are then presented, with this paper focusing on two themes identified as arising across the three research locations. The first of these concerns similarities in the ethno-cultural diversity evident in contemporary high schools in all three of the locations studied and how principals identified the effect of such diversity on their school. The second identifies a number of similarities at to how principals from these ethno-culturally diverse locations perceived and managed their decision-making processes. Finally implications and conclusions drawn from the research are then presented, together with suggestions for further research in this area of contemporary principals’ work.