Thymic injury leads to reduced T cell production and makes patients more vulnerable to infections and cancers. Lemarquis et al. identify a population of recirculating regulatory T (Treg) cells that mediate regeneration in the injured thymus, partially through amphiregulin. An analogous population of Treg cells expressing CD39 and ICOS is found in humans, suggesting therapeutic avenues for boosting thymic regeneration to address aging-and treatment-induced immunosuppression.