The purpose of this study was to develop a career planning program for medical students and to examine its effectiveness with regard to career choice motivation and career maturity. A total of 89 medical students participated in the study. Forty-four were in the experimental group and 45 were in the control group. The collected data were analyzed with the t-test, analysis of covariance, descriptive statistics, and analysis of frequency by PASW SPSS ver. 18.0 (SPSS Inc.). A career planning program was developed using the ADDIE (analysis, design, development, implementation, and evaluation) model. The contents of self-understanding and career exploration were included in this program. The program was conducted as a seminar with preferred major professors. There was a significant difference in the intrinsic motivation score between the control and experimental groups (p<0.05). The score of the experimental group (M=4.59) was higher than that of the control group (M=4.40). Significant differences in decisiveness (p<0.01) and realistic choice (p<0.05), the sub-factors of the career maturity test, were found between the control and experimental groups. The score of decisiveness of the experimental group (M=2.94) was higher than that of the control group (M=2.79). The score of realistic choice in the experimental group (M=3.17) was lower than that in the control group (M=3.37). Most medical students were satisfied with the career planning program. It is hoped that these results provide useful information for designing career guidance programs for students in medical schools.