What distinguishes effective teachers of at-risk or highly mobile students was the essential question addressed in this study. We conducted a cross-case analysis of US national or state award-winning teachers who taught in schools with student populations characterized as highly mobile, homeless, and/or high poverty. Six teachers meeting the criteria were selected as participants. Frameworks of effective teaching characteristics were adapted from prior research and from a review of the literature to gather on-site classroom observational and interview data from participating teachers. The data were examined in light of extant research related to teaching at-risk or highly mobile students and yielded information regarding beliefs and practices. Teachers' interview responses focused on 2 main areas of teacher effectiveness: the importance of student-teacher relationships and instructional delivery. These teachers emphasized affective and academic needs in their planning, instruction, and assessment. They had high expectations of students and were committed to ensuring that students had what they needed to succeed. Teachers maintained high student engagement and used a variety of instructional activities and a wide range of cognitive levels in the questions asked during their instruction which was primarily teacher-directed. Additional research into effective teaching and working with at-risk or highly mobile students is recommended. (Contains 4 tables.)