Glyphosate herbicide has been linked with airway diseases in adults. Evidence remains inconsistent, without investigations conducted in youthful populations. This study aims to examine the association between glyphosate and obstructive airway diseases in adult and youth samples in the National Health and Nutrition Examination Survey. Glyphosate exposure was categorized into tertiles. Separate multiple logistic regressions were conducted for adults and youths, adjusting for relevant covariates. Analyses were stratified by age. Sensitivity analyses explored associations with past-year asthma-related events. In total, 4031 adults and 1692 youths were included. There was a significant dose–response relationship between glyphosate and airway diseases in adults (tertile 2: aOR = 1.17, 95% UI: 0.94, 1.46, p = 0.15; tertile 3: aOR = 1.29, 95% UI: 1.02, 1.62, p = 0.03). Weak associations were shown between glyphosate and asthma in the youth sample (aOR = 1.08, 95% UI: 0.74, 1.58, p = 0.69); however, the relationship was more pronounced in adolescents (aOR = 1.33, 95% UI: 0.82, 2.15, p = 0.24). A dose–response pattern was observed between recent exposure and temporal outcomes in adults, reaching up to 75% higher odds of past-year asthma attacks among participants with glyphosate levels at the third tertile (tertile 3: aOR = 1.75, 95% UI: 0.92, 3.36, p = 0.09). These warrant timely monitoring and prevention strategies, with future research focusing on investigating longitudinal associations.