Previous literature has suggested a link between maternal exposure to atrazine (the most commonly used herbicide in the US) and risk for gastroschisis (a birth defect that involves incomplete closure of the abdominal wall). Our objective was to evaluate the relationship between maternal atrazine exposure and gastroschisis risk by maternal age. We analyzed data for 1,161 cases with isolated gastroschisis and 8,390 controls delivered in Texas from 1999 through 2008. We estimated atrazine exposure based on maternal county of residence and data from the United States Geological Survey. Logistic regression was conducted among all subjects, and separately among offspring of women <25 and ≥25 years. Risk for gastroschisis in offspring was significantly increased for women ≥25 years with high levels of residential atrazine exposure compared to low (adjusted odds ratio: 1.97, 95 % confidence interval 1.19-3.26). This association was not observed among women <25 years. Our results provide additional insight into the suspected relationship of gastroschisis with atrazine. This relationship appears to be different in older versus younger mothers, providing further evidence that the etiology of gastroschisis may vary based on maternal age.