Escherichia coli (E. coli) is a gram-negative bacterium that has economic and public health importance. E. coli strains have been classified into pathogenic and non-pathogenic strains. The pathogenic strains of E. coli can cause colibacillosis, which is a common bacterial disease in the poultry industry and the poultry farms in the region. The objective of the study was to investigate the prevalence of E. coli, its serotypes (O1, O2, O18 and O78) and their antimicrobial susceptibility in the colibacillosis cases in Sulaymaniyah province using culture, antimicrobial susceptibility and molecular approaches. A total of 86 broiler farms were investigated from November 2021 to June 2022. From each farm, samples (liver and heart) were taken from 3-5 broilers colibacillosis cases. The results showed that the colonies that had metallic-green sheen morphologies were positive for E. coli (62/86; 72.1%), in which only 23/62 (37.1%) of the isolates were positive for O2 (7/62; 11.3%), O18 (14/62; 22.6%), and O78 (2/62; 3.2%). While O1 was undetectable in the investigated colibacillosis cases. O18 was predominantly (7/86; 8.1%) detected among 20-30 days-old chickens and followed by O2 (4/86; 4.7%) in 10-20 days-old chickens. The results showed that the majorities of the detected E. coli in colibacillosis cases were isolated from the imported chick from Iran (30; 34.9%) and Netherlands (28; 32.6%). In conclusion, the results showed that the majorites of the colibacillosis cases in the region were caused by E. coli. The E. coli and its serotypes (O2, O18 and O78) had high prevalence in the region.