<p>Drawing on the emotions as social information model, the study examined how teachers’ emotional sharing influenced teaching effectiveness in class. A questionnaire survey of 612 undergraduates, 132 teachers, and 10 research assistants was conducted using the emotional sharing scale, the faking positive emotions scale, the suppression of negative emotions scale, and the student perception of teacher passion and teaching effectiveness questionnaire at a Chinese university. The findings indicated that teachers’ emotional sharing was positively related to students’ perceived teachers’ passion and teaching effectiveness; students perceived teachers’ passion was positively related to teaching effectiveness and mediated the relationship between teachers’ emotional sharing and teaching effectiveness; teachers’ suppressing negative emotions strengthened the positive relationship between teachers’ emotional sharing and students perceived teachers’ passion, and the relationship between teachers’ passion and teaching effectiveness is stronger for senior teachers and students than for junior teachers and students. This study expands the research on teachers’ emotional sharing by revealing its positive effects and influence mechanism on teaching effectiveness, sheds light on teachers’ different emotional labor strategies and highlights the important role of teachers’ tenure and students’ grade in the relationship between perceived teachers’ passion and teaching effectiveness.</p>