Background and Objective: Quail breeders are continuously facing high mortality rates due to Newcastle disease virus infection. Administration of 4-6% Phyllanthus buxifolius leaf powder in the diet can decrease fat and cholesterol levels in egg yolk and increase the immunity of unchallenged quail against Newcastle disease virus. This study examines the effects of P. buxifolius leaf powder on liver function and the haematological responses of quail challenged with Newcastle disease virus. Materials and Methods: One day old quail were acclimatized for 14 days in collective bamboo cages. Seventy-five female quail with similar weights were transferred to individual cages and randomized into five groups, each group being fed a commercial diet containing either 0, 2, 4, 6 and 8% P. buxifolius leaf powder. At the age of 47 days, all quail were infected with velogenic Newcastle disease virus. Haemogglutination inhibition tests were conducted on quail at the ages of 45, 65 and 80 days. Liver function tests and white blood cell and platelet counts were evaluated on quail at the ages of 45 and 75 days. Results: Supplementation with P. buxifolius leaf powder significantly increased antibody titers in 75 and 90 days old quail, significantly decreased aspartate amino transferase and alanine amino transferase levels and decreased total leucocyte, thrombocyte, lymphocyte and monocyte counts. Leaf powders of P. buxifolius have a high potential to protect poultry from infection with Newcastle disease virus and reduce spread of the disease. Conclusion: Dietary supplementation with 4-6% P. buxifolius leaf powder does not cause liver damage or inflammation in quail and may protect against infection. Key words : Liver function, haematological, C. coturnix japonica, Phyllanthus buxifolius, Newcastle disease