OBJECTIVE To determine the effect of asthma controller medication use, choice, and adherence on sleep in children with asthma. DESIGN A case-crossover analysis examining within-subject differences in controller use between time points with and without sleep problems, based on survey data from 3 time points (baseline, 6 months, and 1 year) of a randomized trial. SETTING Families were recruited from 2 area practice networks; all assessments were completed by parents online. PARTICIPANTS Children with asthma, aged 2 to 10 years, as identified by asthma-related medical encounters and prescription fills. MAIN EXPOSURES Parent report of asthma controller medication use (yes/no), type (inhaled corticosteroid or leukotriene inhibitor), and adherence (daily use, nonadherent use, or nonuse). MAIN OUTCOME MEASURES Children's sleep problems, as defined by parent report regarding how often the child had difficulty falling asleep or experienced daytime sleepiness. RESULTS The analysis included 482 children; 82.6% and 75.9% completed the 6-month and 1-year follow-up visits, respectively. Sleep problems were common, with 19.4% of parents at baseline reporting frequent problems with the child falling asleep and 12.1% reporting frequent daytime sleepiness. Compared with children who did not use a controller medication, children had a decreased risk of problems falling asleep during periods with daily controller use (odds ratio [OR], 0.34; 95% confidence interval [CI], 0.13-0.92), with a trend toward an effect in those with nonadherent use (0.47; 0.20-1.12). Any controller use, regardless of adherence, was also associated with decreased odds of daytime sleepiness (OR, 0.69; 95% CI, 0.51-0.94). When controller class was examined, leukotriene inhibitors were associated with significantly decreased odds of problems falling asleep (OR, 0.18; 95% CI, 0.04-0.78), with or without concomitant use of inhaled corticosteroids, but the results for use of inhaled corticosteroids alone were not statistically significant (0.69; 0.32-1.53). CONCLUSIONS Controller medications appear to be effective in reducing sleep problems in children with asthma, and leukotriene inhibitor medications may be especially effective in this population.