Much of the impetus for the burgeoning interest in positive emotions was provided by the influential idea that these emotions play a vital role in the regulation of psychological distress and the maintenance of psychological and physiological homeostasis. Following in these footsteps, the authors review empirical research that highlights the role of nostalgia (a positive emotional state) in the regulation of loneliness (a negative psychological state). Specifically, they propose that the psychological significance of nostalgia resides in part in its capacity to regulate feelings of loneliness by increasing perceived social connectedness. The authors review findings showing that loneliness increases nostalgia and that, in turn, nostalgia increases perceived social connectedness. They then present evidence for the vital implication that, whereas the direct effect of loneliness is to reduce perceived social connectedness, its indirect effect is to increase perceived social connectedness via nostalgia. Finally, they examine how the relation between loneliness and nostalgia is shaped by individual differences that play a governing role in emotion regulation: resilience and the attachment-related dimensions of avoidance and anxiety.