Background: Epidemiologic studies that evaluate the relationship between previous antibiotic use and acute gastroenteritis (AGE) in the pediatric population are currently lacking. Methods: We analyzed inpatient and outpatient children with AGE and healthy controls from Vanderbilt University Medical Center between December 1, 2014, and November 30, 2015. The following 4 outcome groups were defined: overall AGE, norovirus-associated AGE, rotavirus-associated AGE, and nonnorovirus/nonrotavirus AGE. Multiple logistic regression was performed to evaluate the association between previous antibiotic use and the 4 AGE outcomes and with AGE severity. Results: Reported antibiotic use rates in the 3 months before illness onset were similar across the 4 AGE outcomes (overall AGE, 21%; norovirus-associated AGE, 23%; rotavirus-associated AGE, 28%; and nonnorovirus/nonrotavirus AGE, 22%) but were higher than that reported for healthy controls (9%). Compared with healthy controls, patients with AGE overall were 4.6 (95% confidence interval [CI], 1.8-11.4) times more likely to have reported antibiotic use in the 3 weeks before illness onset and 2.6 (95% CI, 1.7-4.1) times more likely to have reported antibiotic use within 3 months before illness onset. Similar results were found for the other specific AGE outcomes. For the overall AGE group, the odds of antibiotic use in the 3 months before illness onset was 3.5 (95% CI, 1.8-7.1) times higher for inpatients than for outpatients. Conclusions: Previous antibiotic use among children was associated with increased odds of AGE, irrespective of etiology, and this association was stronger with more recent antibiotic use. Previous antibiotic use was associated also with more severe AGE.