Background: Infectious diarrhea is one of the most frequent diseases among children, especially in developing countries. Objectives: The aim of this study was to determine the etiological agents and drug resistance patterns of common enteric pathogens isolated in an Iranian 1000-bed tertiary care hospital. Patients and Methods:In a retrospective study, we analyzed the etiology and drug resistance patterns of enteric pathogens associated with diarrheal cases. The study was carried out in the Milad hospital of Tehran over two years, from April of 2012 to January of 2014. Stool specimens from patients with diarrhea (n = 7321) were examined for enteric pathogens using routine microbiological culture methods. Strains of Salmonella, Shigella, and enteric pathogenic E. coli (EPEC) were serotyped and their susceptibility to commonly used antimicrobial agents was determined by a disk diffusion method, as recommended by the clinical and laboratory standards institute (CLSI) guidelines. Results: Enteric pathogens were isolated from 310 (4.23%) of the patients. The most frequently isolated microorganisms included enteropathogenic E. coli (EPEC), Salmonella, and Shigella spp. The majority of the isolates of EPEC were resistant to commonly used antibiotics such as ampicillin (85.61%), cefixime (79.41%), and nalidixic acid. Resistance among other enteric pathogens was also prevalent. About 45.70% of the Salmonella isolates were resistant to chloramphenicol, and 87.95% were resistant to sulfamethoxazole/trimethoprim. Resistance of the Shigella isolates to nalidixic acid in comparison to the resistance recorded in previous studies was higher. Conclusions:The results show that enteric bacteria, including EPEC, Salmonella spp., and Shigella spp. are the major causative agents of diarrhea in the hospital. The emergence of antimicrobial resistance among enteric pathogens is an important problem for public health. Considering the threat of emerging antimicrobial resistance among enteric pathogens, a better surveillance system is necessary.