Educational theories are a constitutive element of educational studies and teacher education. Although not yet researched, it can be assumed that students’ and lecturers’ attitudes and epistemic beliefs about educational theories are relevant prerequisites for high quality learning and instructional processes. To test this claim, we report a mixed-methods study exploring attitudes and beliefs of university students and lecturers about educational theories. We interviewed 32 university students and 12 lecturers and conducted qualitative content analysis. Additionally, the interviewees completed questionnaires about motivational (subjective task value, learning approach and work avoidance goals, interest in educational theories) and affective (enjoyment, boredom, and anxiety when dealing with educational theories) aspects of learning and instruction. The results indicated that educational theories were perceived by both groups to be very abstract and vague. Furthermore, different motivations and emotions were expressed depending on different theory-related attitudes and beliefs. Participants with positive attitudes reported stronger task-value and learning goals, weaker work avoidance goals, more interest, and more enjoyment and less boredom than participants with negative attitudes about educational theories. These associations were quite strong and found for both students and lecturers. Depending on the participants’ beliefs on educational theories, we found primarily differences in motivations and emotions for students and not for lecturers. Taken together, the results point to the importance of theory-related attitudes and beliefs for learning and instruction, as disentangling their interrelations with motivational and affective processes could help to better describe, explain, and foster individual educational professionalization.