Using an explanatory sequential mixed methods approach, this secondary analysis investigated the relations among classroom dialogic interaction, fifth-grade students' reading achievement, and teachers' dialogic stances. First, quantitative analyses of time-sampled lesson observations and state reading test scores suggested that the more class time teachers spent facilitating dialogic interaction directly promoted student reading performance. Qualitative analyses extended quantitative findings by examining lesson transcripts and teacher interviews from three exemplar cases: two extremely high in classroom dialogic interaction and one extremely low. Results indicated that the highly dialogic teachers had a dialogic stance that prioritized student background knowledge and incorporated student voice into discussions. These teachers enacted their stance through the use of specific dialogic discursive moves. The less dialogic teacher did not demonstrate a dialogic stance, used classroom talk to control students, and transmit information within the observed lesson. These results offer insights into how and why teachers use dialogic interaction and the mechanisms behind interaction's effect on student achievement.