Medical Professionalism (MP) defined as values, behaviours and attitudes that promote professional relationships, public trust and patient safety is a vital competency in health profession education. MP has a distinctive uniqueness due to cultural, contextual, conceptual, and generational variations. There is no standard instructional strategy to probe the understanding of MP in a cohesive, structured, interactive manner. This study aimed to investigate undergraduate medical students' understanding of MP using express team-based learning (e-TBL) at both campuses of Royal College of Surgeons Ireland (RCSI). Using the key principles of a sociocultural theoretical lens in adult learning theory, we designed e-TBL as a context-learning-based educational strategy. We conducted three e-TBL sessions on cross-cultural communication and health disparities, a reflective report on clinical encounters, and professionalism in practice. We collected, collated, and analyzed the student experiences qualitatively using data gathered from team-based case discussions during e-TBL sessions. A dedicated working group developed very short-answer questions for the individual readiness assurance test (IRAT) and MP-based case scenarios for team discussions. In this adapted 4-step e-TBL session, pre-class material was administered, IRAT was undertaken, and team-based discussions were facilitated, followed by facilitator feedback. A qualitative inductive thematic analysis was performed, which generated subthemes and themes illustrated in excerpts. Our thematic analysis of data from 172 students (101 from Bahrain and 71 from Dublin) yielded four unique themes: incoming professional attitudes, transformative experiences, sociological understanding of professionalism, and new professional identity formation. This qualitative study provides a deeper understanding of medical students' perceptions of medical professionalism. The generated themes resonated with divergent and evolving elements of MP in an era of socioeconomic and cultural diversity, transformative experiences, and professional identity formation. The core elements of these themes can be integrated into the teaching of MP to prepare fit-to-practice future doctors.