Chronic pain is among the most prevalent health issues experienced by older adults and negatively impacts daily functioning and psychosocial well-being through mechanisms that include energy depletion, pain interference, and pain-related changes in negative affect. The capacities to be aware of and regulate negative emotions play a critical role in the successful management of chronic pain. One dimension of negative emotion awareness, termed negative emotion differentiation (NED), is the ability to discriminate between negative affective experiences and recognize them as discrete categories. The ability to identify and distinguish between the various emotions that accompany pain flares and other stressors may enhance the precision of the individual’s regulatory efforts. In doing so, NED may be one possible resilience resource that can facilitate adaptive functioning in the context of chronic pain by buffering the effects of chronic pain flares on daily interpersonal stress. However, this has not yet been investigated. The current study aimed to examine the moderating effect of trait NED on the relationship between daily pain and same-day stress in 259 patients diagnosed with osteoarthritis (OA) or fibromyalgia syndrome (FMS). Individuals completed daily diaries each evening for 30 days reporting on average daily pain, negative emotions, interpersonal stress, and depressive symptoms. It was hypothesized that higher levels of NED would buffer the effects of daily pain on same-day stress. In exploratory analyses, it was evaluated whether the buffering effects were larger for individuals with FMS versus OA. Results of multilevel models revealed that, as expected, higher levels of trait NED predicted lower levels of same-day negative interpersonal events and perceived interpersonal stress. Trait NED also moderated the relationship between pain-related increases in same-day perceived interpersonal stress. Additionally, findings indicated that NED was similarly important for those with FMS and OA. Taken together, the current findings suggest that NED is an important resilience trait that can attenuate chronic pain-related increases in daily experiences of interpersonal stress.