Recent evidence suggests negative associations between received social support and emotional well-being. So far, these studies mainly focused on younger adults. Quantity and quality of social support changes with age; therefore, this study investigated whether there are age differences regarding the association between received social support and positive affect (PA) and negative affect (NA). Moreover, it was tested whether these age effects might be due to a differential effectiveness of different sources of support for younger and older individuals. Forty-two individuals (21 younger adults, aged 21–40 and 21 older adults, aged 61–73) completed 30-daily diaries on their received social support, PA/NA and the sources of support provision. Data were analyzed using multilevel modeling. Results indicated age-related differential effects: for younger individuals, received social support was negatively associated with indicators of emotional well-being, whereas these associations were positive for older respondents. Regarding NA, these effects held when testing lagged predictions and controlling for previous-day affect. No age differences emerged regarding the associations between different sources of support and indicators of affect. Conceptual implications of these age-differential findings are discussed.