What does it take to become effective teachers of students of culturally, ethnically, linguistically, and racially diverse backgrounds? Based on research with teachers over the past several years, this paper discusses what it means to teach students of diverse backgrounds with heart, courage and conviction, and the implications of their practice for professional development. A review of relevant literature finds that some of the widely acknowledged qualities of effective teachers include a solid general education background; a deep knowledge of subject matter; familiarity with numerous pedagogical approaches; strong communication skills; and effective organizational skills. Although these qualities are essential for good teaching, the purpose in this paper is to suggest that they are insufficient because they fail to take into account the sociopolitical context of education as well as the tremendous diversity of language, social class, ethnicity and race, among other differences, that are a fact of life in many school systems around the world. An additional set of qualities is proposed that are also essential for teaching in the postmodern industrialized and interdependent world. These have to do with attitudes, sensibilities and values. The author describes what she has found to be some of the qualities of teachers who make a positive difference in the lives of students, particularly students who have been marginalized by their school experiences. These qualities include a sense of mission; solidarity with, and empathy for, their students; the courage to challenge mainstream knowledge and conventional wisdom; improvisation; and a passion for social justice. The paper ends with implications for intercultural education and teacher education.