This study was designed to investigate the efficacy of essential oils as an alternative prophylaxis and treatment for avian aspergillosis. The in vitro susceptibility of Aspergillus fumigatus, A.flavus, and A.niger strains to antifungal drugs ( Nystatin, Amphotericin B (AMP ), Ketoconazole (KTC ), Itraconazole (ITR) and Fluconazole (FLU), and to essential oils (Garlic, thyme, cinnamon, tea tree, clove and chamomile oils) was determined using the macro diffusion methods. All fungal isolates demonstrated variable degrees of drugs resistances. All fungi showed 100% resistance to fluconazole, while ketoconazole is highly effective than itraconazol, amphotericin B and nystatin in all isolated fungi. Essential oils showed antifungal effect especially cinnamon oil followed by clove and garlic among tested EOs in vitro. Cinnamon oil showed the highest inhibition zone diameter to all fungi, so it was chosen for experimental trial based on the obtained antifungal activity results, Cinnamon oil was highly effective against A.fumigatus infection with a dose of 1 ml \ kg ration and could be used in the field of poultry instead of other antifungal drugs.