Herein we report a murine model to examine transplacental transmission, transmammary transmission, or both, of Neospora caninum. Prevalence of transplacental transmission in outbred Swiss-Webster mouse pups was 85%, with 11 of 13 litters containing at least 1 transplacentally infected pup. Sixty-two percent of litters born to experimentally infected dams contained 85% or more transplacentally infected pups. Numbers of pups congenitally infected per litter was higher if dams were inoculated during the first half of pregnancy. Transplacental transmission decreased to 25% when a singly infected dam delivered a second litter. Transmammary transmission was observed in 1 of 51 pups suckling dams experimentally infected 5, 10, or 15 days postparturition. No pups were infected when cross-fostered onto chronically infected dams.