Concerned with the interplay between the self and close relationships, we examined whether nostalgia, a wistful affection for one’s past, enhances self-esteem indirectly by fostering social connectedness. We also explored the boundaries of this effect across demographic, cultural, and situational contexts. Across four experiments, we manipulated nostalgia using either a guided recollection exercise (i.e., Event Reflection Task; Experiments 1–3) or a virtual reality induction (Experiment 4). In a life-span sample (Experiment 1; N = 441), a cross-cultural sample spanning 28 regions (Experiment 2; N = 2,521), a Gazan sample facing chronic adversity (Experiment 3; N = 416), and a Prolific sample subjected to a virtual reality manipulation (Experiment 4; N = 128), nostalgia reliably increased social connectedness, which in turn predicted higher self-esteem. The indirect pathway from nostalgia to self-esteem via social connectedness was robust across gender, age, and cultural indicators (i.e., individualism–collectivism, wealth, life expectancy, happiness). These findings paint nostalgia as a universally social emotion that bolsters self-esteem through heightened perceptions of belonging, even under adverse conditions. The results clarify both the psychological mechanisms and the contextual limits of nostalgia’s benefits.