Abstract: Population census of Pteropus giganteus (Brünnich, 1782) with relation to climatic conditions in Thazi, Mandalay Region in Central Myanmar was executed from July, 2015 to June, 2018. The initial population size of P. ginanteus was recorded as 545.69 ± 55.63 individuals during first study period (July, 2015 - June, 2016) and 638.16 ± 35.81 individuals in second study period (July, 2016 - June, 2017). The population size was gradually increased to 655.53 ± 29.65 individuals in third study period (June, 2017 - July, 2018). Positive correlation was established between population size of P. giganteus and climatic conditions such as ambient temperature, relative humidity and rainfall. Relation between ambient temperature and monthly mean population size was positive (R² = 0.042, R² = 0.1015, R² = 0.236) in three study periods. Positive correlation between relative humidity and monthly mean population size revealed to (R² = 0.0029, R² = 0.0261, R² = 0.0481). The result of correlation between rainfall and monthly mean population size was occurred (R² = 0.1506, R² = 0.2629, R² = 0.1457) respectively during three years study.