We examined age and control belief differences in physical and emotional reactivity to daily stressors in four domains: interpersonal, work, network, and home. We combined data from the National Study of Daily Experiences and the Midlife in the United States survey, resulting in 1,031 participants who reported on 7,229 days. Findings from multilevel models suggest that age and control beliefs play an important role in a person's reactivity to interpersonal, network, and work stressors. Specifically, older age and lower perceived constraints were each related to lower emotional and physical reactivity to interpersonal stressors. High mastery buffered the physical effects of work stressors for younger and older adults, and high mastery was important for middle-aged adults' emotional reactivity to network stressors. High constraint was associated with the strongest physical reactivity to network stressors for younger and older adults.