Single-cell suspensions derived from immature rodent and ungulate testes can reconstitute testicular cords upon grafting into immunodeficient mice. In the present study, neonatal common marmoset monkey (Callithrix jacchus) testes were digested to a single-cell suspension, which was transplanted subcutaneously into immunodeficient mice. After 9 or 18 weeks of incubation, the derivatives of the grafted single-cell suspensions were retrieved and analyzed histologically and immunohistochemically. Three of 4 (75%) neonatal grafts exhibited reconstituted seminiferous cords strongly resembling seminiferous cords of the intact neonatal testis. The cords consisted of Sertoli cells, germ cells and peritubular myoid cells, which was confirmed by immunohistochemical marker analysis. Three-dimensional reconstruction models of the grafts revealed elongated tubules. Some of the tubules were branched, which occurs also in vivo, as we show here for the marmoset monkey. Importantly, no teratoma formation by immature pluripotency factor-expressing germ cells was observed. In summary, the reconstituted testicular cords were almost indistinguishable from the cords formed in situ, thereby impressively demonstrating a very high reconstructive potential of a single-cell suspension obtained from the neonatal marmoset monkey testis. To our knowledge, this is the first study demonstrating testicular cord neomorphogenesis for a primate species ex situ.