Background: This study was conducted to examine the effect of the motivational interviewing smoking cessation program on nicotine dependence, smoking-related attitude, and abstinence self-efficacy in inpatients with mental disorders. Methods: The study design was a nonequivalent control group non-synchronized pre-posttest design. The study was conducted from June 1, 2015, to May 15, 2017. The participants were psychiatric inpatients who were currently smoking. Twenty-five people in the experimental group and 22 people in the control group participated in the program. The program was conducted twice a week, for 60 minutes per session, for a total of 3 weeks. Results: There were statistically significant differences in smoking-related attitude and abstinence self-efficacy between the experimental and control groups. However, there was no statistically significant difference in nicotine dependence. Conclusions: Based on the results, the motivational interviewing smoking cessation program can be applied to change smoking attitude and to enhance self-efficacy in quitting smoking of inpatients with mental disorders.