Purpose. The purpose of this study was to examine the effects of a rehabilitation program on hope and self-efficacy in a sample of homeless adolescent substance abusers at a halfway house in Seoul, Korea. Methods. Five residents of a halfway house were provided with a 16-week rehabilitation program based on a cognitive-behavioral approach. To evaluate the effectiveness of the program, this study used a single-case experimental design with the variables - hope and self-efficacy - being measured at pre-, post-, and follow-up tests. Results. While three participants showed considerable positive changes in hope and self-efficacy after the program, two participants did not show any positive changes. Despite this lack of consistent patterns in the effectiveness of the rehabilitation program, there was a qualitative change in social status (such as academic and work status) for the participants at the follow-up test. Conclusion. A rehabilitation program based on a cognitive-behavioral approach may improve the hope and self-efficacy of homeless adolescent substance abusers at a halfway house and help them to reintegrate into society.