Objective: The main objective of this study was to study the effect of stocking density in two genetic groups of rabbits (purebred Californian (CAL × CAL) and Californian × Rex (CAL × RX) crossbred rabbits) on growth performance, some blood hematological, biochemical and immunological parameters and carcass traits. Materials and methods: A total of 120 weaned rabbits were randomly assigned to a completely randomized design with a 2 × 3 factorial arrangement of treatments (two genetic groups; 60 of each CAL × CAL and CAL × RX and three stocking densities; 8, 12 and 20 rabbits/m 2 ; the number of rabbits under each stocking density was 24, 36 and 60; respectively) and 6 replicates. Results: The effects of genetic group × stocking density interactions were significant (P<0.05) on most of growth performance traits, blood biochemical parameters and phagocytic activity, whereas the effects were non-significant on majority of blood hematological parameters and carcass traits. CAL × CAL rabbits stocked at 20 rabbits/m 2 had the lowest final body weights and total average daily gains, but had the highest feed to gain ratio. CAL × CAL rabbits stocked at 20 rabbits/m 2 had the lowest total protein and the highest glucose, corticosterone, liver function tests, and total antioxidant capacity (TAC). Conclusion: CAL × CAL rabbits stocked at 20 rabbits/m 2 recorded higher liver and kidney function tests, glucose, TAC, corticosterone levels and lower phagocytic activity which refers to the response of this genetic group to the stress of this higher stocking density and subsequently lower growth performance was observed in these rabbits.