Avian cellulitis causes significant losses to the poultry industry. Avian-pathogenic Escherichia coli (APEC) is the etiological agent of that disease. This microorganism has zoonotic potential and may act as reservoir of antimicrobial-resistance genes. In this context, the production of extended-spectrum B-lactamase (ESBL) is one of the main antimicrobial resistance mechanisms. The objective of this study was to determine the production of ESBL in an Escherichia coli (E. coli) strain isolated from avian cellulitis lesions. Twenty-two E. Coli isolates were harvested from cellulitis lesions in chicken carcasses in a commercial processing plant. Isolates were then submitted to virulence genotypic profile (iutA, hlyF, iss, ironN, ompT) analysis, antimicrobial susceptibility test, and detection of ESBL production. The results showed that 22.7% of the isolates presented five virulence genes, 9.1% four genes, 36.4% three genes, 13.6% two genes, and 18.2% one gene. The tested isolates showed resistance to ampicillin (90.9%), ceftiofur (54.5%), gentamicin (45.5%), tetracycline (72.1%), sulfamethoxazole/trimethoprim (54.5%), and enrofloxacin (54.5%). Furthermore, 77.3% of the isolates presented multidrug resistance (MDR) profile and 72.7% were positive for ESBL production. This study is the first description of ESBL-producing APEC isolated from avian cellulitis lesions, which suggests the need to establish efficient APEC control measures and programs to prevent flock productivity losses due to colibacillosis and public health risks.