Copyright © 2014 by the American Association for Laboratory Animal Science. Many attempts have been made to culture germ cells in vitro by mimicking their development in vivo. The objective of this study was to establish an alternative method of xenotransplantation by developing a new approach for the rapid induction of spermatogenesis by using the chorioallantoic membrane of developing chicken embryos. Fertilized chicken eggs were incubated for 7 d, after which a small window was cut into the shell of the egg. We then transplanted testes from 7- to 8-d-old B6D2F1 mice onto the vessels of the chorioallantoic membrane and incubated them at 35.0 °C for 14 d or 37.5 °C for 12 d. After this in ovo CAM (iCAM) culture, the survival rates of the eggs and testes were assessed histologically and immunohistologically. The transplanted testes in the chicken embryos that survived were supported by the CAM, with an associated chronic vascularization response. The testes cultured at 35.0 °C had lower rates of generation and higher rates of death than did those cultured at 37.5 °C. Histologic examination of the testes cultured at 37.5 °C revealed the presence of spermatogonia and primary spermatocyte-like germ cells in the seminiferous tubules. The number of cells positive for synaptonemal complex protein 3 in the seminiferous tubules was significantly higher than that in the noniCAM-cultured testes from control mice. These results suggest that iCAM culturing of neonatal donor testis induces androcyte development. This method could be the foundation for a method that would enable in vitro spermatogenesis.