The disease caused by Pasteurella multocida is an extremely common and difficult issue of rabbits utilized for biomedical research. The vaccination techniques are dependably the most powerful preventive measures. In the present study, 30 New Zealand rabbits (1.5 kg average body weight and 6–8 weeks old) were divided into 3 groups, control group (I), challenged non- vaccinated group (II), and challenged double vaccinated group (III). 1st dose was administered at the 1st day followed by similar booster dose after 21 days. At the end of the 2nd , 4th , and 6th weeks of the experiment, blood samples were collected from the ear vein for hematological, plasma, and serum examination. At the end of the 6th week, the rabbits were anaesthetized and sacrificed to collect the tissue specimens from liver, kidneys, spleen, lungs and heart for histopathological study. The results showed that double immunization with killed vaccine of P. multocida increased the immune response of the animals and the leukocyte phagocytic activity against P. multocida and also improved the clinicopathological and histopathological findings. Taken together, our findings proved that double immunization with killed vaccine of P. multocida increased the phagocytic activity of the immune cells and the immune status of animals against infection.