Aging of cardiac stem/progenitor cells (CSCs) impairs heart regeneration and leads to unsatisfactory outcomes of cell-based therapies. As the precise mechanisms underlying CSC aging remain unclear, the use of therapeutic strategies for elderly patients with heart failure is severely delayed. In this study, we used human cardiosphere-derived cells (CDCs), a subtype of CSC found in the postnatal heart, to identify secreted factor(s) associated with CSC aging. Human CDCs were isolated from heart failure patients of various ages (2–83 years old). Gene expression of key soluble factors was compared between CDCs derived from young and elderly patients. Among these factors, SFRP1, a gene encoding a Wnt antagonist, was significantly up-regulated in CDCs from elderly patients (≥65 years old). sFRP1 levels was increased significantly also in CDCs, whose senescent phenotype was induced by anti-cancer drug treatment. These results suggest the participation of sFRP1 in CSC aging. We show that the administration of recombinant sFRP1 induced cellular senescence in CDCs derived from young patients, as indicated by increased levels of markers such as p16, and a senescence-associated secretory phenotype. In addition, co-administration of recombinant sFRP1 could abrogate the accelerated CDC proliferation induced by Wnt3A. Taken together, our results suggest that canonical Wnt signaling and its antagonist, sFRP1, regulate proliferation of human CSCs. Furthermore, excess sFRP1 in elderly patients causes CSC aging.