Although humor is frequently used in face‐to‐face courses and computer‐based training, there is no consensus in the literature on its effects on students' learning. The aim of the present study was therefore to assess the cognitive effects of adding humorous drawings in a computer‐based course on both learning outcomes and learning behaviors (eye movements). It was assumed that humorous drawings would improve learning through the active resolution of incongruity. To isolate this effect from those of the illustrations, a nonhumorous drawings condition was also compared with the text‐only condition. Eye‐movement data showed that humor increased visiting duration for the drawings. Learning outcomes were not affected by the nonhumorous drawings, whereas humor had a positive effect on comprehension, though not on retention. This effect of humor was not mediated by visiting time for the slides. Our results argue in favor of the use of content‐relevant cartoons to improve students' learning.