Since elementary school is a time in which basic concepts like attitudes and mindsets about careers are formed, career education is very important to elementary school students. This study was conducted to investigate the effects of a gardening program applying the academic disciplines of Science, Technology, Engineering, Arts, Mathematics, and Society (STEAMS) on developing career education for elementary school students. In order to determine the effectiveness of the program on career development of elementary school students, this study was conducted with 28 upper elementary students in the experimental group who participated in the gardening program, and 30 upper elementary students in the control group who did not. The program was comprised of total 8 sessions, one session per week, with various garden activities. The career development scores of the two groups before and after the program were comparatively analyzed. Before the program, the experimental group had significantly lower scores for career development than the control group. After 8 weeks of the program, the control group did not show any changes in career development, while the experimental group that participated in the program showed a significant increase in career development, resulting in no difference in career development between the two groups after the program. Therefore, the program has positive effects on improving career development of upper elementary students who previously had insufficient career development. Overall, the program had positive effects on career development of upper elementary students, and further research is needed to systematically promote the STEAMS-based gardening program to promote interest and understanding of students by associating plant-based gardening activities with various subjects such as science, art, and social studies.