In the spring of 2023, several "broiler breeder" and "broiler" farms in North Lebanon were affected by a disease that impaired general performance and caused severe daily mortalities. Despite antibiotic treatments, there was no significant improvement. Serological analysis indicated that the flocks were protected against Infectious Bursal Disease (IBD), Infectious Bronchitis Virus (IBV), Avian Influenza (AI), and Newcastle Disease Virus (NDV). However, necropsy revealed severe liver lesions and swollen kidneys. This study investigated the possible presence of avian adenovirus (FAdV), which causes inclusion body hepatitis, and avastrovirus (AstV), which causes hepatitis and runting stunting syndrome, in Lebanese breeders and broilers. For the first time, a co-infection between FAdV and AstV was described. Both viruses were detected by PCR and RT-PCR. DNA sequencing identified the FAdV as adenovirus E type 8b and adenovirus D type 2 and the AstV as avastrovirus type 2. This comprehensive study identified the primary cause of the atypical body inclusion hepatitis and runting stunting syndrome observed in North Lebanon.