In this study, we present the newly developed "Misconceptions about Multimedia Learning Questionnaire" (MMLQ), we evaluate its psychometric properties (item difficulties, scale reliabilities, and internal structure), and we use it to examine the prevalence of four different misconceptions about multimedia learning in student teachers and teachers. A total of 311 participants (176 teachers and 135 student teachers) responded to the items of the MMLQ. The results revealed moderate reliabilities of the MMLQ scales. Moreover, an a priori assumed four-factor structure of misconceptions about multimedia learning was most compatible with teachers' and student teachers' answers to the MMLQ items. These four factors were "learning styles" (multimedia instruction needs to be adapted to students' learning styles [visual or auditory]), "hemispheric isolation" (multimedia instruction enables hemispheric communication), "naïve summation" (multimedia instruction is more effective the more sensory channels are used), and "motivation primacy" (multimedia instruction is mainly effective because it is motivating). The majority of teachers and student teachers endorsed three of the four misconceptions about multimedia learning (i.e., learning styles [78.1%], hemispheric isolation [58.8%], and naïve summation [81.4%]) as assessed by the MMLQ. This finding may provide valuable information for teacher education and training regarding this specific issue.