This study investigated the relation between preschoolers' mobile electronic device (MED) use and sleep disturbances. A national sample of 402 predominantly college-educated and Caucasian mothers of 3-5-year-olds completed a survey assessing their preschoolers' MED use, bedtime resistance, sleep duration, and daytime sleepiness. Heavier evening and daily tablet use (and to some extent, smartphone use) were related to sleep disturbances. Other forms of MED use were not consistently related to sleep disturbances. In addition, playing games on MEDs at bedtime was related to compromised sleep duration, although other forms of MED use at bedtime were not related to sleep outcomes. Although the relations between MED use and sleep disturbances were small in size, they were larger than the relations between sleep and other predictors in the models. Continued work should investigate how MED exposure is related to children's cognitive, psychological, emotional, and physiological development, particularly given the popularity and widespread use of these devices.