Negative social exchanges have the potential to detract from well-being in later life, but the factors that influence older adults' vulnerability to such exchanges remain poorly understood. Two dimensions of vulnerability, exposure and reactivity, were investigated using daily diary data collected at two time points from a sample of community-residing older adults (N = 129). Three categories of predictors were examined: individual characteristics, life stress, and social network characteristics. Greater exposure to negative social exchanges was related to greater life stress and to less supportive networks. Greater reactivity was related to lower self-esteem, less supportive networks, less satisfying friendships and family relationships, and surprisingly, to less life stress. Longitudinal changes in exposure and reactivity were related to changes in friendship satisfaction, the positive functions performed by the network, and health status. The findings suggest that personal characteristics and life circumstances play a role in influencing older adults' vulnerability to negative social exchanges.