This cross-sectional, observational study examined whether objectively measured physical activity (PA) and specific activities are associated with loneliness and social isolation (SI) in rural-living older adults. A total of 112 participants (M_age = 72.8 [SD = 6.6], 51.8% female) from 23 villages in Wiltshire, United Kingdom, completed questionnaires, 7-day accelerometry, and activity diaries. Regression analysis was used to test associations between objectively measured light PA, moderate to vigorous PA, and total PA; loneliness; and SI from family, neighbors, or friends and to explore these associations using specific activities. Daily mean light, moderate to vigorous, and total PA were not associated with loneliness or SI. Volunteering, accompanying others, and sports/exercise were associated with lower SI from neighbors (odds ratio = 0.23, 95% CI [0.06, 0.91]), family (odds ratio = 0.39, 95% CI [0.22, 0.68]), and friends (odds ratio = 0.56, 95% CI [0.33, 0.97]), respectively. There were no associations between loneliness, SI, and objectively measured PA. The contribution of PA to loneliness and SI needs to be further investigated with larger and diverse samples of rural-living older adults.