We aimed to develop a horticultural therapy program to prepare adolescents at the Dae san juvenile detention center (D-JDC) for their return to society. The effects of the program on emotional stability and career exploration were investigated. Adolescents who wished to participate in the horticultural therapy program were recruited from the D-JDC. Data were collected using various questionnaires before and after the program was implemented. Thirty-five (mean age, 15.74 ± 1.65 years; 11 males, 24 females) students were enrolled. The program mainly consisted of plant cultivation activities, such as seeding, transplanting plants, cutting, harvesting, and post-harvest utilization. To evaluate emotional health, the ego-resiliency scale was used. To evaluate social behavior, the inventory of parent and peer attachment, peer attachment scale, and social skills scale were used. Career exploration was assessed using the career preparation behavior scale and the career decision-making self-efficacy-short form. Peer attachment, social skills, and career preparation behavior showed significant improvements after the program, with the students responding positively in the post-program surveys. Our horticultural therapy program helped improve the career exploration and social skills of D-JDC students and positively affected their emotional stability. Based on our findings, horticultural therapy can be used as a correctional program for adolescents in D-JDC to help them return to society.