The human grief response has perplexed researchers. Grief is costly, leading to painful and potentially deleterious symptoms. Yet, it is a human universal. We argue that grief functions as a hard-to-fake signal of underlying capacities to form strong social bonds. If so, those who grieve more intensively than others should be perceived as higher quality social partners. We tested this hypothesis in 4 studies. High grievers were rated as nicer, more loyal, and more trustworthy than low grievers. High grievers were also expected to cooperate in a prisoner’s dilemma more than low grievers. Last, high grievers were chosen as a trusted social partner more than another individual who expressed sadness for lost material items, indicating that grief may be a specific display of distress that is particularly informative to potential social partners. These results support a signaling theory of grief and are discussed in that context.