This study investigates undergraduate microwave engineering students' conceptions of electromagnetic (EM) wave propagation using a phenomenographic approach. An in-depth semi-structured interview was used to examine a cohort of 15 students' experience of EM wave propagation in the context of microwave engineering. Result of the study revealed five qualitative distinct categories of students' conceptions. These categories evolved from a basic understanding of EM wave as oscillations of electric and magnetic fields to a comprehensive interpretation of wave propagation as radiation and energy transfer. Students' cognitive processes of awareness, discernment, and simultaneity were evident within the descriptive categories. Besides, four dimensions of variation highlighted how students' understanding evolved from basic awareness to discerning complex relationships between concepts. The findings also offer practical implications for designing effective instructional strategies as well as theoretical support for the application of phenomenography in exploring students' learning experiences. Finally, teaching implication for microwave engineering education was presented.