We implemented screening of children 16–30 months of age (n = 1,760) from a typically under-served, primarily Hispanic, population, at routine pediatric appointments using the modified checklist for autism in toddlers (M-CHAT) and Ages and Stages Questionnaire. Screen positive rates of 26 and 39 %, respectively, were higher than previous reports. Hispanics were more likely to score M-CHAT positive than non-Hispanics (adjusted OR 1.7, 95 % CI 1.2–2.4), as were those screened in Spanish. About 30 % of screen-positive children were referred for further assessment, but only half were seen. Thus screening in this population is feasible, but may require additional resources. Attention to the cultural applicability of screening instruments, as well as to explaining the results or need for additional services to parents, is critical to serve the growing Hispanic population.