Objective: To determine whether screening children in an urban pediatric emergency department (PED) would lead to identification of previously undiagnosed developmental delay. Methods: This was a cross-sectional study of families presenting to an urban public hospital PED with children 6 to 36 months and no history of developmental delay. Children were screened for possible developmental delay using the Ages and Stages Questionnaire; parents completed an instrument that assesses 5 domains: communication, gross motor, fine motor, problem solving, and personal-social. Sociodemographic data were also obtained. Results: One hundred thirty-eight children were enrolled, all accompanied by their mothers. Mean age of the children was 18.9 months; 51.5% were female; 56.8% of the mothers were high-school graduates; 59.9% were immigrants; 75.4% were Latino. Twenty-one percent did not have a regular source of primary care; 26.8% (95% confidence interval, 20.1%-34.8%) screened positive in at least 1 domain, with a trend toward the highest percentage of positive screens on the communication domain (z = 1.89, P = 0.059). In a simultaneous multiple logistic regression model including all predictor variables, child age of 12 to 30 months was associated with increased adjusted odds of positive screen (adjusted odds ratio, 8.4; 95% confidence interval, 1.4-48.9). Having a primary caregiver born in the United States was statistically significant for screening positive in at least 1 Ages and Stages Questionnaire domain (P = 0.03). Conclusions: Almost 30% of 6- to 36-month-old children presenting to an urban PED without prior developmental concerns screened positive for possible delay, suggesting the utility of performing routine developmental screening in the PED. Pediatric emergency department use alone may be an indication for screening. Further study is needed for feasibility of screening for delay in the PED.