Feeding protein-rich forage rice irrigated with treated municipal wastewater for fattening pigs at 5-6 months of age was reported to improve the quality of its meat in our previous study. However, this feeding practice has a concern regarding the potential transmission of antimicrobial-resistant bacteria and resistance genes from the treated wastewater to the pigs. In this study, we investigated the antimicrobial resistance of Escherichia coli isolated from 9 pigs (test) at 6 month of age, which were fed the wastewater-irrigated forage rice for 55 days, at a pig farm in Yamagata, Japan, comparing the isolates from other 9 pigs (control) fed the same cultivar of rice produced in the conventional farming practice. Forty-three strains of E. coli were isolated from the fecal samples collected from 16 of 18 fattening pigs, including 22 strains from 8 test pigs and 21 strains from 8 control pigs. Antimicrobial susceptibility testing revealed 24 of 43 isolates, with 10 isolates from 5 test pigs and 14 isolates from 7 control pigs, were resistant to tetracycline, chloramphenicol, kanamycin, ampicillin, or sulfamethoxazole/trimethoprim. No significant difference in resistant rates to any of these five antimicrobials were found between the test and control pigs (p > 0.05). The 24 isolates of resistant E. coli were characterized by the detection of antimicrobial-resistance genes using PCR analysis and the classification using multi-locus sequencing typing. Twelve types of resistance genes associated with the above five antimicrobials were detected from the isolates, with the similar profile between test and control pigs. Moreover, the resistant isolates were classified into six sequence types (STs), which were consistent across the two groups of pigs. These findings suggest that feeding the wastewater-irrigated forage rice to fattening pigs at 5-6 months of age caused negligible impacts on the occurrence of antimicrobial resistant E. coli in their intestines.