OBJECTIVES: To examine whether (a) negative social encounters and physical pain are linked throughout the day, (b) negative mood mediates these associations, and (c) these associations vary by closeness with social partners. METHOD: Adults aged 65+ (n = 313) completed ecological momentary assessments and reported their negative social encounters, physical pain, and mood every 3 hr throughout the day for 5-6 days. RESULTS: Multilevel models revealed that negative social encounters were associated with greater pain at each 3-hr interval and that this association was mediated by negative mood during the same interval. Negative encounters with less close partners were associated with pain, but negative encounters with close partners were not. DISCUSSION: Regulating older adults negative emotions may be crucial to improving their daily pain. Further, interventions focusing on negative encounters with less close partners in daily life may help mitigate older adults experiences of pain throughout the day.