This randomized controlled trial was conducted to evaluate the effects of a 3-month-long Chan-Chuang qigong program on patients' physical performance and quality of life while excluding the influence caused by the progression of their cognitive impairment. Patients with mild to moderate cognitive impairment were recruited from two dementia daycare centers in Taiwan. The control group (n = 41) received the standardized plan of treatment, and the qigong group (n = 39) received the standardized plan of treatment plus the Chan-Chuang qigong program. The outcomes were muscle strength, muscle endurance, exercise capacity, and quality of life. After controlling for the progression of cognitive impairment, the qigong group showed significant improvements over the control group and baseline in muscle strength and exercise capacity at Months 2 and 3 (p < 0.05) and in muscle endurance at Months 1, 2, and 3 (p < 0.05). The Cognitron test scores were significantly associated with muscle strength (p = 0.03), whereas the Corsi block-tapping test scores were significantly associated with exercise capacity (p = 0.001). Furthermore, a significant between-group difference was detected in the physical (p = 0.01), not mental (p = 0.83), component of quality of life. The 3-month Chan-Chuang qigong program can be applied for patients with mild to moderate cognitive impairment as complementary therapy to improve their muscle strength, muscle endurance, exercise capacity, and physical quality of life. This program should be practiced for at least 2 months to achieve satisfactory results.