[Purpose] The aim of this study was to examine the effects of exercise therapy on the health-related QOL of people with knee osteoarthritis. [Subjects] Four databases (PubMed, Cochrane Central Register of Controlled Trials, the Physiotherapy Evidence Database, and the Cumulative Index to Nursing and Allied Health Literature) were searched for randomized controlled trials that evaluated the effects of exercise therapy on health-related QOL assessed by the SF-36 for inclusion in our systematic review. The methodological qualities of the trials were assessed independently by two reviewers using the PEDro scale. Pooled analyses with a random-effects model or a fixed-effects model were used in the meta-analyses to calculate the standardized mean differences and 95% confidence intervals. [Results] Twelve studies met the inclusion criteria. Our meta-analysis provides high-quality evidence that exercise therapy increases the summary score, physical functioning score, and role-physical score of knee osteoarthritis sufferers. Our meta-analysis also provides moderate-quality evidence that the physical component summary and mental component summary scores were improved to a greater extent by exercise therapy than by control interventions. [Conclusion] Exercise therapy can improve health-related QOL, as assessed by the SF-36, of knee osteoarthritis sufferers. Keywords: Exercise; Health-related quality of life; Knee osteoarthritis.