The aim of the study was to assess the effectiveness of specially designed, empathy training for medical undergraduates, based on the principles of Person-Centered Approach. Within the context of the humanistic person-centered patient care, the experiential, 60-hour "Empathize with me, Doctor!" training program contains theory, personal development and skills development. Role plays, experiential exercises, self-awareness exercises, active listening practice and conduction of a person-centered interview constituted the training. Forty-two medical undergraduates (66% females; 29% fourth year of study, 40% fifth, 31% sixth) from the University of Ioannina in Greece applied and all of them completed the empathy training. Forty-five medical students comprised a similar according to age and year of studies control group. The Jefferson Scale of Physician Empathy (JSPE) was used to assess the empathic performance, and Cohen's d to assess the practical importance of any statistical difference. The JSPE mean score (and standard deviation) before, after and six months follow-up was 109.3(12.7), 121.1(9.0), 121.1(9.5), respectively. The before-after and before-follow-up difference was highly significant (CI95%, p<0.001 in both cases), and of great practical importance (d = 1.072, d = 1.052, respectively), while no decrease was observed six-months later (CI 95%, p = 0.999, d<0.001). Control group reached a JSPE 108.7(10.5), similar to intervention group before training (CI95%, p = 0.832), and highly different and important compared to after (CI 95%p<0.001; d = 1.268) and follow-up (CI 95%, p<0.001; d = 1.238) intervention scores. The "Empathize with me, Doctor!" improved significantly and importantly medical undergraduates' empathic performance, which was maintained intact for at least six months.