In recent decades, the number of studies on the occurrence of resistant strains in wildlife animals has increased significantly, but data are still fragmentary. The aim of this study was to evaluate drug resistance of Escherichia coli strains isolated from wild carnivorous mammals, common in Poland. Selective media with antimicrobials (tetracycline, kanamycin, chloramphenicol, and cefotaxime) were used for isolation. Of 53 isolates shown to be distinct by the amplification of DNA fragments surrounding rare restriction site-fingerprinting method, 77.8% were multidrug-resistant (multidrug-resistant). All strains were resistant to ampicillin and many of them also exhibited resistance to tetracycline (76.2%), sulfamethoxazole (57.1%), streptomycin and kanamycin (49.2%), chloramphenicol (30.1%), and nalidixic acid (46%). In most cases, the phenotypic resistance profile was confirmed by detection of relevant genes mostly occurring in strains isolated from livestock animals and humans. Extended-spectrum β-lactamase-producing strains were detected in one mink and three martens. The strains were carriers of blaTEM-1,blaTEM-135, and blaCTX-M-15 genes. Our research confirmed a high carrier rate of MDR E. coli, even more than one MDR strain in a single individual; therefore, wider monitoring in this group of animals should be considered.