This study was designed to determine if a male physical educator’s appearance of body fatness affects his ability to teach and instill good exercise intentions in high school students. Subjects, 850 students in six schools, viewed one of two 20-minute videotapes in which exercise concepts were presented. The tapes were identical with one exception: In one of the tapes the instructor’s body dimensions were altered by a “fat suit.” Immediately after seeing their tape, the students completed a content examination and questionnaire. Analysis of variance revealed that the viewers of the overweight instructor’s tape scored lower on all aspects of the examination (p < .01). Also, t tests done on their responses to the questionnaire revealed that the students exhibited a lesser intent to exercise (p < .01) and rated less favorably the teacher’s likability, expertise, and appropriateness as a role model (p < .01). Analysis of 2 × 2 (Instructor Appearance × Students Self-Perceived Fitness Levels) ANOVAs done on the students’ intent to exercise, liking of the instructor, appropriateness of the instructor as a model, and knowledgeability of the instructor revealed no interactions (p > .01). It was concluded that a male physical educator’s appearance may be a very powerful mediator of teaching effectiveness. Further ideas for study in this area were suggested and possible implications for teacher education schools were made.