Quantum theory is one of the most successful theories in physics. Because of its abstract, mathematical, and counter-intuitive nature, many students have problems learning the theory, just as teachers experience difficulty in teaching it. Pedagogical research on quantum theory has mainly focused on cognitive issues. However, affective issues about student learning are just as important as cognitive issues. The purpose of this study was to investigate pre-service physics teachers' motivation towards learning quantum theory by examining motivational constructs such as expectancies, values, ability beliefs, and goals. The participants (n = 6) of this case study were fourth-year pre-service physics teachers at a state university in Turkey. Through semi-structured interviews, the participants were asked seventeen questions that focused on motivational constructs. Analysis of the qualitative data indicated that the instructor, nature of the content, and previous performance were three motivational elements that originated in the context of the quantum mechanics course. Furthermore, these context-dependent elements interacted with the other elements of motivational constructs in both direct and indirect ways. Because unsuccessful learning situations are explained by low motivation, context-dependent affective elements and their interactions should be considered in the teaching and learning of quantum theory.