Abattoir wastewater is a major source of pollution burden and life-treating human pathogenic bacteria. The aim of this study was to determine the extended-spectrum β-lactamase-producing (ESBL) producing E. coli isolates and their antibiotic resistances in wastewater samples. In this experimental study, abattoir wastewater samples were collected and identified from 32 different regions in Mazandaran Province, North Iran. Disk agar diffusion test was applied for testing antibiotic resistance. Phenotypic detection of ESBL-producing isolates was performed using combined disk method. The presence of blaSHV gene was investigated using PCR method. The prevalence of E. coli in wastewater samples was 10%. The ESBL test analysis was positive for 14 (93.33%) isolates. The prevalence of blaSHV gene in ESBL-producing E. coli isolates was 93.34%. The highest antibiotic resistances in ESBL-producing E. coli were found concerning to ceftizoxime and gentamicin (100%), nalidixic acid, ceftazidime and ciprofloxacin (93.34%). Nitrofurantoin was the most effective antibiotic against E. coli isolate exhibiting the highest sensitivity (73.34%). In conclusion, the prevalence of ESBL-producing E. coli is high and being increased. The high prevalence of blaSHV gene in these isolates may be a reason for their pathogenesis and ability in transferring the resistance genes to multiple antibiotics. Therefore, there is a need to develop appropriate treatment and safer disposing abattoir wastes in this province.