Purpose: Senior centers are focal points of services and programs. Study aims were to describe the frequency of and benefits of attending senior centers and nonmembers’ reasons for nonattendance. Methods: A total of 597 senior center members and 298 community-residing nonmembers in New York City were interviewed. Males and age of 75+ years members were oversampled. Results: Mean days attended weekly = 3.00 days/week (SD = 1.71). Latinx seniors attended 1 day > White non-Latinx seniors. Seniors in poor/bad health attended .67 fewer days than seniors in excellent health. Almost all members (96.3%) reported benefiting from attendance. The most common benefits were socialization/making friends, educational programs, something to do, being with people like them, meals, and improved mental and physical health. Reasons nonmembers gave for nonattendance were too busy with social/leisure activities or work, not interested or do not need programs/services, do not want/need socialization, and members were older or more disabled than them. Conclusion: Implications for recruiting underserved and isolated seniors are discussed.