Using instructional humor processing theory, in an online learning setting we explored the relationships between instructor humor types as perceived by students and the students' learning engagement. This study recruited 1,829 participants. The results revealed the following: (a) Course-related, courseunrelated, self-disparaging, and aggressive instructor humor were associated with behavioral, emotional, and cognitive engagement; (b) positive emotions mediated the relationships between course-related, course-unrelated, and aggressive instructor humor styles and students' behavioral and cognitive engagement; (c) negative emotions mediated the links between all four types of instructor humor, and behavioral and cognitive engagement. This study is the first to extend the theoretical model of instructional humor styles to the online learning environment, verifying the adaptability of the theory to China.