Aging takes place in a social context but older adults also spend a significant amount of their time alone. Solitude (the objective state of being alone and without social interaction) has been associated with negative experiences but also with specific benefits. We examine the importance of social relationships for time-varying associations between affective experiences and solitude. Using repeated daily life assessments from an adult life span sample (Study 1, N = 183, age: 20-81 years) and an older adult sample (Study 2, N = 97, age: 50-85 years), we examined the moderating role of social relationship quality on within-person solitude-affect associations. Data were analyzed using multilevel models controlling for gender, age, overall amount of time in solitude, retirement status, marital status, education, and current work activity. Higher relationship quality was associated with higher average affective well-being. Compared to being with others, participants reported lower levels of high-arousal positive affect (PA) during solitude in both studies. In Study 1, solitude was also associated with higher levels of low-arousal negative affect (NA) and higher levels of low-arousal PA compared to when with others. Across both studies, individuals with higher quality relationships reported lesser increases in low-arousal NA when in solitude, as compared to individuals with lower quality relationships. Findings highlight that solitude is experienced less negatively for individuals embedded in a context of higher quality social relationships. Thus, preservation and promotion of social resources in older adulthood may be important to ward off potential negative ramifications of spending a significant amount of time alone. (PsycINFO Database Record