Haematological profile is important to determine the physiological condition of an individual, and morphology of red blood cells can also be helpful in making a diagnosis of a disease. The size of red blood cells affects the ability of red blood cells to carry oxygen. In some clinical events shape and size of red blood cells will be changed. Bats are the only mammals that have the ability to fly. The ability of bats to fly would require bats to be able to bind more oxygen, therefor bat should have enough of energy while flying. The present study was conducted on 12 Cynopterus tithaecheilus (7 males and 5 females) to study about haematological profile. Blood samples were taken using tuberculin needle and analyzed by hematology analyzer for hematological value. Size of red blood cells was taken using bloods smear and analyzed by imageJ software. Cynopterus tithaecheilus show the higher number of red blood cells, but the size were smaller compared to the other mammals which has same body size. Mean while the concentration of hemoglobin and hematocrit were higher. The present result suggested that these haematological values might provide a greater transport oxygen capacity in the Cynopterus tithaecheilus.