The objective of this study was to evaluate the effects of closed breeding on some reproductive performance of a small commercial Japanese quail flock which had been closed bred for ten years. Seventy two laying female birds at 3 months of age were obtained from the commercial flock and randomly separated into 2 groups (closed and crossbreeding). Closed group was mated with their own male, crossbreeding group mated with males that bringing from different flock to form the first generation animal material and then each group mated with their own male to form second generation animal material in a ratio of 1 male 3 female. From these mates 250 eggs were collected and stored at 15 degrees C and incubated at 37,5 degrees C 70% RH when the birds were at the 3 months old of age in each group and generation. Mean egg weight, embryonic mortality, weak offspring rate and albino birds rate were significantly higher and fertilized eggs rate, hatchability, survival rate and hen day egg production were lower in the closed group than crossbreeding group in both generations. The results indicated that viability and reproductive performance were decreased due to inbreeding in small and closed flock. As a conclusion, crossbreeding Should be occasionally done for ameliorating the negative effects of inbreeding in small and closed flocks.