Fowl adenoviruses (FAdVs) are important pathogens in poultry, responsible for significant economic losses. FAdV serotypes are known by their resistance to chloroform and ether. High temperatures reduce the efficiency of disinfecting poultry farms. So, biosecurity measures and efficient management practices are very important to control and prevent FAdVs. This study aimed to compare the efficiency of Chicken Embryo Fibroblast (CEF) and Chicken Embryo Liver (CEL) cells for propagation of three FAdV serotypes (FAdV 8a, 8b, and 11) to evaluate different chemical agents for virus inactivation. The virus was cultured in both cell types under identical conditions, and viral titers were measured using embryonated chicken eggs with PCR. CEL cells demonstrated significantly higher virus yields compared to CEF, with a greater TCID₅₀ value and more distinct cytopathic effects, indicating superior support for viral replication. Following propagation, inactivation trials were conducted using various agents, including formalin at different concentrations. Among these, 0.2% formalin was the most effective, achieving complete viral inactivation while preserving antigenicity, as confirmed by safety testing in embryonated eggs. These findings suggest that CEL is the preferred system for high-titer FAdV propagation, and 0.2% formalin is a reliable inactivation method suitable for inactivated vaccine production.