Purpose: The purpose of this study was to assess the association between Adult Day Health Center (ADHC) participation and health-related quality of life. Design and Methods: Case-controlled prospective study utilizing the Medical Outcomes Survey Form 36 (SF-36) to compare newly enrolled participants from 16 ADHC programs with comparable community-dwelling older adults who did not attend an ADHC. Assessments were conducted at study enrollment, 6 and 12 months. Results: ADHC participants (n = 57) and comparison group subjects (n = 67) were similar at baseline in age, ethnic diversity, medical conditions, depression, cognition, immigration history, education, income, and marital status. Significantly more comparison group subjects lived alone (p = 0.002). One year after enrollment, the SF-36 domains role physical and role emotional improved significantly. Adjusted role physical scores for ADHC participants improved (23 vs. 36) but declined for the comparison group (38 vs. 26, time by group interaction p = 0.01), and role emotional scores improved for ADHC participants (62 vs.70) but declined for the comparison group (65 vs. 48, time by group interaction p = 0.02). Secondary analyses revealed that changes in daily physical functioning, depressed affect, or cognitive functioning did not explain the improvements found in role physical and role emotional scores for ADHC participants. No significant differences in trends for the 2 groups occurred for the SF-36 domains physical functioning, social functioning, and mental health. Implications: ADHC participation may enhance older adults' quality of life. Quality of life may be a key measure to inform care planning, program improvement, and policy development of ADHC.