Based on self-concept, role experience, and readiness to learn andragogy's assumptions, this phenomenological research identifies the types of instructional strategies that professors use in a mixed undergraduate classroom to benefit traditional students' and adult learners' active participation in the classroom. The majority of studies emphasize that professors tend to manage instructional strategies, such as lecture or presentations, in mixed undergraduate classrooms mainly by focusing on traditional students' characteristics such as age, role experience, expectations, and motivations. The findings of this study indicate that professors who have more adult learners in their mixed undergraduate classrooms tend to adapt and apply student-centered strategies, such as interactive lectures, group discussions, or debates in higher level classes, based on both traditional and adult learners' characteristics.