Teaching effectiveness is often evaluated through student ratings of instruction (SRI). Research suggests that there are many potential factors that can predict student's perceptions of teaching effectiveness such as professor-student rapport, student engagement, and perceived humor of the instructor. Therefore, we sought to assess whether undergraduate student's perceptions of professor-student rapport, student engagement, and humor predict scores on retrospective SRIs. The findings suggest that professor-student rapport is the largest predictor (54% of variance) of scores on SRIs, while humor and student engagement were significant, but minor predictors of SRIs. Since SRIs are often used by administration to determine hiring, promotions, and tenure decisions for faculty, understanding what predicts SRIs is important to both faculty and administrators of higher education.