Aim: To examine the effect of a 6-month, smartphone app-based self-management program for people with chronic obstructive pulmonary disease (COPD). Background: Technological interventions have been used for chronic disease management, but the effect of a self-management program using a smartphone app has not been evaluated in people with COPD. Methods: For this randomized controlled trial, patients with COPD (N = 44) were recruited in pulmonary medicine outpatient clinics at two, metropolitan, tertiary care, academic hospitals. Eligible participants were randomized into two groups and received group education and exercise sessions in the first month of the 6-month intervention. Participants in the experimental group received a smartphone app-based self-management program, which included education, exercises, self-monitoring of symptoms and exercise, and social support. Participants in the control group received one call a month from the research staff. Self-care behavior was measured as a primary outcome. All measures were administered at baseline and at 6 months. Results: After randomization, the experimental group numbered 22, the control group numbered 20, and 2 participants dropped out. Significant differences between groups were found in change score for self-care behavior, total activity count per wear time, and percent time spent in moderate-to-vigorous physical activity over 6 months. Conclusion: A self-management program, using a smartphone app, can effect behavioral change in people with COPD. This program could be a boon to patients with COPD who have limited access to a health care provider, no opportunities for pulmonary rehabilitation, and frequent exacerbations.