Using a multilevel approach, this study examined the role of classroom emotional climate on students' academic achievement. Positive and negative emotions and homeroom teachers' support were used to assess the classroom emotional climate on the individual and class levels. To our knowledge, no study to date has investigated these specific aspects of the classroom emotional climate in relation to students' GPA. Data were collected from 73 classrooms in grades 7-12 (N = 1,641, students; 53% female) across three schools in Israel. Findings revealed that aggregated levels of both positive affect and perceived homeroom teacher support were positively tied to GPA and that aggregated levels of negative affect were negatively tied to GPA. The final model included gender, teacher support, individual and class emotions and explained 14% of within-class GPA. A central implication of this study is the relevance of having an emotionally supportive homeroom teacher for students' academic achievement.