Many Hispanics in the United States have limited English proficiency and prefer communicating in Spanish. Language barriers are known to adversely affect health care quality and outcomes.We explored the relationship between parent language preference in a Hispanic population and the likelihood that a child with symptoms receives a diagnosis of asthma.We conducted a school-based survey in 105 Chicago public and Catholic schools. Our sample included 14,177 Hispanic children 6 to 12 years of age with a parent who completed an asthma survey. Outcomes of diagnosed asthma and possible asthma (asthma symptoms without diagnosis) were assessed by using the Brief Pediatric Asthma Screen Plus instrument.Overall, 12.0% of children had diagnosed asthma, and 12.7% had possible asthma. Parents of children at risk who completed the survey in English reported higher rates of asthma diagnosis compared with parents who completed it in Spanish (55.2% vs 36.3%, P < .001). Predictors of asthma diagnosis were child sex, parental language preference, parental asthma status, and other household members with asthma.Parental language preference might be an important characteristic associated with childhood asthma diagnosis. Whether language itself is the key factor or the fact that language is a surrogate for other attributes of acculturation needs to be explored.Our findings suggest that estimates of asthma among Hispanic schoolchildren might be low because of underdiagnosis among children whose parents prefer communicating in Spanish.