Coarse particle matter, PMcoarse, is associated with increased respiratory morbidity and mortality. The aim of this study was to investigate the association between short-term changes in PMcoarse and sub-clininal airway inflammation in children. Healthy children aged 11 years from two northern Swedish elementary schools underwent fraction of exhaled nitrogen oxide (FENO) measurements to determine levels of airway inflammation twice weekly during the study period from 11 April–6 June 2011. Daily exposure to PMcoarse, PM2.5, NO2, NOx, NO and O3 and birch pollen was estimated. Multiple linear regression was used. Personal covariates were included as fixed effects and subjects were included as a random effect. In total, 95 children participated in the study, and in all 493 FENO measurements were made. The mean level of PMcoarse was 16.1 μg/m3 (range 4.1–42.3), and that of O3 was 75.0 μg/m3 (range: 51.3–106.3). That of NO2 was 17.0 μg/m3 (range: 4.7–31.3), NOx was 82.1 μg/m3 (range: 13.3–165.3), and NO was 65 μg/m3 (range: 8.7–138.4) during the study period. In multi-pollutant models an interquartile range increase in 24 h PMcoarse was associated with increases in FENO by between 6.9 ppb (95% confidence interval 0.0–14) and 7.3 ppb (95% confidence interval 0.4–14.9). PMcoarse was associated with an increase in FENO, indicating sub-clinical airway inflammation in healthy children.