The goal of this study, which was carried out in 2022 in the Advanced Entomology Laboratory of the Department of Biology, Girls College of Education, University of Kufa, was to determine how well the fungus filtrates of Alternaria alternata affected the mortality percentages of house fly larvae and pupae, Musca domistica. The results indicated an increase in the mortality percentages of larvae in the first and third instar of the house fly, Musca domistica with increasing concentrations used. In the study, the highest mortality percentages were recorded after three days of treatment with a concentration of 10%  (100 and 85%) in the first and third instar larvae, respectively. The effect of the fungus filtrates on some biological aspects when treating the third instar larvae of houseflies, as it led to a decrease in pupation percentages to 15% when treating pupae with a concentration of10%, and the pupal deformation percentages to 10% and a decrease in adult emergency percentages to 0%. when treating pupae with the fungus filtrates of Alternaria alternata at a concentration of 10 %, which increased the pupal deformation to 80% and decreased adult emergency percentages to 20%.