This study aims to validate the effectiveness of general high school teachers’ competency enhancement training program for guiding career and academic design according to the introduction of the high school credit system. To this end, a three-session competency enhancement training program for guiding career and academic design was developed. Through a brief description of the program to a general high school in J area, a program to visit 13 general high school sites voluntarily applied was operated and its effectiveness was verified. 183 out of total 227 participating teachers responded to both pre- and post-test and a paired t-test was conducted on the data of 183 teachers. The results of the pre-post paired sample t-test showed a significant increase in the overall self-efficacy on career guidance of the participating teachers, as well as in the sub-factors of process confidence, evaluative ability, and influence. These effects were significant across all genders, work experience, age groups, and school locations. Also, the satisfaction level of the participating teachers was high, with no significant differences on gender, work experience, age group, or school location. Finally, there was a significant correlation between the value of career guidance self-efficacy on career guidance post-test score minus pre-test score and program satisfaction. General high school teachers’ competency enhancement training program for guiding career and academic design developed in this study proved effective in enhancing teachers' self-efficacy on career guidance, and the participating teachers expressed high satisfaction with the program. Implications and limitations of this study and suggestions for follow-up studies were discussed.