Most children don’t get enough sleep (Dement, 2005; Maas, 2011), and 77% of preschoolers experience sleep related disruptive behaviors at least a few nights per week (National Sleep Foundation, 2004). Sleep is especially crucial during early development to promote health, education, brain development, physical growth, and quality of life. Insufficient sleep is a public health problem, and this is clearly true for young children (CDC, 2015). The National Institutes of Health reported that preschoolers need 11–12 hours of sleep daily (NIH, 2012). Good sleep hygiene includes consistent bedtimes and morning rising times, and avoiding large meals, caffeine, and light sources (e.g., night lights, smart phones, iPads, computers) before bedtime (CDC, 2015). Three memory tests, a sleep hygiene scale, a socioemotional assessment, and height and weight measurements (to calculate BMI) were administered to preschoolers. Following testing, Fitbit devices were worn on each child’s ankle for the 12-week data collection period. Fitbit parameters included steps per day, total activity time, and time of day at which most physical activity occurred (morning, afternoon, or evening). Sleep quality and sleep habits parameters included number of restless minutes, awake minutes, total hours spent sleeping nightly, child’s bedtime, and the child’s wake time. We hypothesized that more physically active children would experience better sleep quality, a later bedtime, and an earlier wake time than children who are less physically active. We also hypothesized that children who are most active in the evening would exhibit better sleep quality than children who are most active in the morning or afternoon. We expect better sleep quality to be associated with higher scores on cognitive and socioemotional measures. Results provide greater knowledge regarding the association between sleep, physical activity, and biopsychosocial outcomes that may be useful in implementing better education for parents and children geared toward improving sleep