Many modern theories of affect recognize two fundamental underlying affective dimensions, although the precise dimensions vary. Alongside positive (PA) and negative (NA) affect, social safeness, a warm soothing affect associated with caring and attachment processes, has been proposed as a third fundamental affective dimension (Gilbert et al., 2008). The present work aims to establish whether social safeness is indeed distinguishable from PA, NA, or their combination. A cross-sectional study consisting of self-report measures of PA, NA, and social safeness was conducted in a sample of 1889 community participants recruited from Mechanical Turk. Shared variance among latent PA, NA, and safeness was examined using correlation and regression analyses. Next, two longitudinal studies of 93 and 99 college students investigated the relationships of these three constructs with perceived stress and perceived, received, and given support. Both between-persons and within-person analyses supported the hypothesis that social safeness is an affective dimension in its own right that can be meaningfully distinguished from PA and NA. Social safeness was associated with moderately higher PA and lower NA. It uniquely predicted stress and social support outcomes controlling for PA and NA.