Background: Mentorship is a critical component of medical education and professional development. Effective mentorship supports academic achievement, clinical competence, research productivity, leadership development, and career satisfaction among medical students and healthcare professionals. Objective: To evaluate the influence of mentorship on medical career development, including academic performance, clinical competency, research engagement, leadership skills, and professional satisfaction. Methods: A cross-sectional mixed-method study was conducted among 320 medical students, residents, and early-career physicians from three teaching hospitals. Data were collected using structured questionnaires, mentorship assessment scales, and semi-structured interviews. Statistical analyses included descriptive statistics, chi-square tests, and multivariate regression analyses. Results: Participants with active mentors demonstrated significantly higher academic performance (88.6% vs. 74.3%), research participation (76.2% vs. 41.7%), leadership involvement (69.4% vs. 35.1%), and career satisfaction (91.2% vs. 67.8%) compared with those without mentors (p < 0.001). Qualitative findings revealed that mentors provided guidance in career planning, emotional support, networking opportunities, and professional identity formation. Conclusion: Mentorship significantly contributes to medical career advancement by enhancing professional competencies, academic success, research engagement, and personal development. Structured mentorship programs should be integrated into medical education and healthcare institutions.