Using a multi-method, multi-level approach, this study examined the link between classroom emotional climate and student conduct, including as a mediator the role of teacher affiliation, i.e., students' perceptions of their relationships with their teachers. Data were collected from 90 fifth- and sixth-grade classrooms (n = 2,000 students) and included classroom observations, student ratings of teacher affiliation, and conduct grades on report cards. As predicted, when controlling for teacher characteristics and the organizational and instructional aspects of the classroom, there was a direct, positive relationship between classroom emotional climate and conduct that also was mediated by teacher affiliation. Effects were robust across grade level and student gender. We highlight the role of emotionally supportive classroom environments in promoting teacher affiliation and better conduct among students. (Contains 2 tables and 1 figure.)