This paper proposes the Instructional Humor Processing Theory (IHPT), a theory that incorporates elements of incongruity-resolution theory, disposition theory, and the elaboration likelihood model (ELM) of persuasion. IHPT is proposed and offered as an explanation for why some types of instructor-generated humor result in increased student learning and others do not. A preliminary study was conducted with 378 students who identified a specific instructor and reported that same instructor's use of inappropriate and appropriate humor, perceptions of instructor humorousness, and affective learning and learning indicators. The Instructional Humor Processing Theory hypothesized that humor related to instructional content would correlate positively with student learning, while inappropriate forms would not. Consistent with IHPT, related humor, an appropriate form of instructional humor, was positively associated with student learning, while other-disparaging and offensive humor, inappropriate forms of humor, did not correlate with student learning. Humorous instructors used significantly more appropriate and inappropriate humor than nonhumorous instructors. Explanations are offered for these findings as well as study limitations and directions for future research to support IHPT. (Contains 1 figure, 2 tables and 1 note.)