Prolonged loneliness can be detrimental to both mental and physical health. However, variability in how individuals respond to loneliness can shape health outcomes. Here, we explored whether loneliness is related to perceptions of support and strain given in family and friend relationships. Specifically, we assessed whether resting parasympathetic nervous system (PNS) activity, a marker of emotion regulation and flexible adaptation, moderates self-evaluation of support and strain given. Participants were from the Midlife Development in the US (MIDUS) dataset who had measures of loneliness, perceived support given and perceived strain given in relationships, and resting PNS activity. Loneliness was associated with decreased support and increased strain given in both family and friend relationships. Resting parasympathetic activity moderated the relationship between loneliness and strain given to family, with lower PNS activity associated with a stronger relationship. These findings contribute to our understanding of how loneliness shapes social perception.