Antimicrobial overuse contributes to antimicrobial resistance. Empiric use of antimicrobials for diarrheal illness is warranted only in a minority of cases, because of its self-limiting nature and multifactorial etiology. This study aims to describe the factors contributing to antimicrobial overuse for diarrheal disease among children less than 5 years of age in rural Bangladesh. A total of 3,570 children less than 5 years of age presenting with diarrhea in a tertiary level hospital were enrolled in the study. The rate of antimicrobial use at home was 1,395 (39%), compared with 2,084 (89%) during a hospital visit. In a multivariate analysis, factors associated with antimicrobial use at home included residence located more than 5 miles from a hospital; use of zinc and oral rehydration salts at home; vomiting; greater than 10 stools per 24 hours; diarrheal duration greater than 3 days; and rotavirus diarrhea ( < 0.05 for all). Characteristics of children more likely to be given antimicrobials in a health-care setting included greater than 10 stools per 24 hours; duration of diarrhea greater than 3 days; use of antimicrobials before hospital presentation; fever (≥ 37.8°C); rectal straining; and infection ( < 0.05 for all). The most commonly used drugs in rotavirus diarrhea were azithromycin and erythromycin, both before hospital presentation and during hospital admission. Our study underscores the importance of diligent vigilance on the rationale use of antimicrobials both at home and in health-care facilities with a special concern for children less than 5 years of age living in rural Bangladesh.