Infectious bronchitis (IB) is considered to be one of the major causes of economic loss in the chicken production sector in many countries including Egypt, even in vaccinated flocks. In the present study, tracheal swabs and different organs (trachea, paranasal sinuses , bronchi , lung and kidney) were collected from 30 broiler farms showing respiratory signs and variable mortalities in different localities of Behira governorate at the period from January 2017 to March 2020 in order to determine the genetic changes occurred in hypervariable region I and II of S1 gene of IBV and also the pathological changes associated its infection. The virus was isolated then detected by real-time RT-PCR in the fore mentioned samples. About 56.7% (17/30) from the investigated farms were positive for IBV infection. S1 gene has been partially sequenced for three recent isolates and phylogenetic analysis revealed close relatedness with each other. These isolates belong to genotype 1- lineage 23 (G1- 23), and shared less than 84.4% and 79.5% nucleotide and amino acid identities, respectively, with the commercial vaccine strains used in Egypt. The study also showed similar pattern of viral evolution to IBV at Egypt and Israel. Pathological examination of paranasal sinuses, trachea and bronchi revealed the presence of mucous exudate, epithelial erosion in some cases and hyperplasia in others. Lung showed severe interstitial pneumonia while kidneys showed multiple focal areas of necrosis with lymphocyte aggregation. It can be concluded that IBV strains isolated from Beheira governorate are distinct from vaccine strains and should be included in vaccine production that will help in improving IBV control.