An important part of online courses is the delivery of instruction via video lectures. Video lectures should use media effectively to reduce extraneous load and maximize cognitive processing, thereby helping students to learn. Instructors may be able to reduce extraneous load by varying the number of audio and visual media used. This study presents analysis from a survey of students (n = 1701) enrolled in a cyber university in South Korea to investigate the relationship between media diversity in video lectures and extraneous load. Results showed a negative relationship between media diversity and extraneous load. Students who noted more types of media stated that they experienced less extraneous load. The implications of these results are of use to instructors who want to use diverse media to promote a better understanding of learning material.