This study evaluated the effect of a tailored stage-matched intervention designed to increase exercise among Korean adults with chronic diseases. A physician and a nurse collaborated to deliver the intervention to 21 patients; the control group (CG) consisted of 20 patients. A nonequivalent CG pretest-posttest design was used. On follow-up, commitment to a plan for exercise was significantly greater in the intervention group (IG) than in the CG. Furthermore, the proportion of the IG in the active stage was significantly increased compared to that of the CG. The results suggest the potential of a stage-matched intervention program for increasing commitment to physical activity and for promoting progress through stages of exercise among patients with chronic diseases in a physician-based Korean clinic.