The effect of cryopreservation and subsequent xenotransplantation on the follicular reserve of the canine ovary by using non obese diabetic-severe combined immunodeficient (NOD-SCID) mice was examined. Vitrified-warmed canine ovarian tissues were placed into the ovarian bursa of mice, and then were removed and subjected to histological examination at 4 weeks after the transplantation. Over 30% of primordial follicles and 65% of early primary follicles survived after cryopreservation. However, regardless of breed or age, percentages of survived primordial follicles and early primary follicles after the transplantation ranged from 0–7% and from 0–15%, respectively. These results indicate that the majority of primordial follicles and early primary follicles in vitrified-warmed canine ovarian tissues disappear after xenotransplantation. Further studies will be required to be able to enhance the survival of transplanted cryopreserved ovarian follicles in canine.