Infectious bronchitis virus is one of the most important economic viral diseases of poultry that is spreading worldwide, affects both gallinaceous and non-gallinaceous birds. Avian Pathogenic Escherichia coli (APEC), classified under the extra-intestinal pathogenic E. coli (ExPEC) category which causes various syndromes in poultry including systemic and localized infections. Infectious bronchitis and E. coli diseases caused by pathogens are considered infectious or contagious because they can be transmitted from poultry to poultry through direct and indirect routes. According to their pathogenic microorganism, they can be biologically classified into viruses, bacteria, fungi, parasites and protozoa. There was total of “Ross strain” chicks used in this study was 21000, (1.523) chickens died resulting in an overall mortality rate of (7.5%) chicken. There were changes in clinical symptoms that occur in broiler chickens aged 10-15 days. These changes include respiratory signs such as difficulty breathing, cough, depression, and decreased appetite. There were changes in post mortem that occur in broiler chickens aged 12, 16 and 31 days. Those changes include mild congestion in the trachea at (12 day of age), congestion in the lung at (16 days of age), nodules and thick surface in the proventriculus and mild congestion in the ileocecal junction at (31 days of age), the lesions that appear were suspected of the infectious bronchitis disease. The study was conducted to determine the prevalence and incidence of an Infectious bronchitis and E. coli pathogens of significant economic importance in broiler farm at Kirkuk City, Iraq. At the end, the results obtained from this work also confirm the suitability of postmortem changes in infectious bronchitis virus and E. coli bacteria included mild congestion in the trachea and proventiculus, also fibrinous peri-hepatitis and pericarditis in broiler chicks.