Background: Postgraduate medical education faces increasing challenges related to expanding medical knowledge, large trainee cohorts, and the need to develop teamwork and clinical reasoning skills. Team-Based Learning (TBL) is an active learning strategy designed to address these challenges, yet evidence in postgraduate Internal Medicine training remains limited in resource-constrained settings. Objective: To evaluate the effectiveness and feasibility of Team-Based Learning among postgraduate trainees in Internal Medicine at the Defence Services Medical Academy. Methods: A cross-sectional descriptive study was conducted following a TBL-oriented session on obesity-related medical conditions. Sixty-nine second- and third-year postgraduate trainees were organized into 12 teams. Peer and tutor evaluations of individual performance were collected using a structured questionnaire assessing preparation, knowledge contribution, respect for others’ ideas, and flexibility. Descriptive statistics were calculated, and inferential analyses included paired-sample t-tests and one-way ANOVA. Qualitative feedback was analyzed thematically. Results: Most teams demonstrated above-average or outstanding performance based on peer ratings. Paired-sample t-tests revealed statistically significant differences between peer and tutor ratings (p < 0.05). One-way ANOVA demonstrated significant inter-team variability in performance scores (p < 0.01). Qualitative findings indicated enhanced teamwork, self-directed learning, clinical reasoning, and communication skills. Both trainees and tutors reported positive perceptions of TBL feasibility and educational value. Conclusion: Team-Based Learning is an effective and feasible instructional strategy for postgraduate Internal Medicine education. Its implementation promotes active participation, teamwork, and application of knowledge, supporting its integration into postgraduate medical curricula, particularly in settings with limited faculty resources.