The influence of a positive relationship with the teacher on students' academic achievement is well established in the literature. However, little is known about how teachers' sentiments regarding students' physical appearance may influence this relationship. The purpose of this study was to examine the possible relationships between teacher feelings and emotions, the teacher-student relationship, and student academic achievement and the mediating role of the student-teacher relationship between teacher's sentiments and students' achievement. The sample consisted of 40 teachers and 566 students. The NRC Emotion Lexicon, the Student-Teacher Relationship Scale and self-reported GPA data were collected. A mediation analysis with a multicategorical antecedent was conducted. Results shows that the student teacher relationship played a mediating role between teacher's sentiments and student performance. The results illustrate the influence of teacher emotions on student achievement and provide teachers and researchers with a comprehensive knowledge of the effects of emotions on the student-teacher relationship.