This study examined awareness of and knowledge of how to address increasing linguistic and cultural diversity among 89 teachers in an ethnically and racially diverse school located in Southwest Finland. The empirical evidence suggests that in a school with many years of experience with a diverse student population the levels of awareness and knowledge among teachers are relatively low and teachers themselves expressed the need for much more information, in particular, strategies for meeting the needs of their students. In addition, teachers showed distinct levels of awareness of diversity which successively predicted their knowledge of strategies for addressing diversity in the classroom. Implications for research and teacher education are discussed.