Intercultural understanding (ICU) is becoming an essential part of living and contributing effectively in our increasingly diverse society. In fact, ICU is a key capability in the Australian schooling curriculum, alongside other general capabilities such as numeracy and literacy. While there are current instruments assessing ICU, there is little evidence-based research surrounding their use in primary and secondary school settings. In the context of a larger project, this study outlines the development and validation of a new ICU instrument specifically for use in primary and secondary schools. Among a sample of teachers and students from 12 Australian primary and secondary schools, the study found a teacher ICU instrument with a four-factor structure and a student ICU instrument with a two-factor structure. Further research and implications are discussed.