Nocturnal sleep has been shown to benefit memory in adults and children. During the preschool age range (~3-5 years), the distribution of sleep across the 24-hour period changes dramatically. Children transition from biphasic sleep patterns (a nap in addition to overnight sleep) to a monophasic sleep pattern (only overnight sleep). In addition, early childhood is a time of neuronal plasticity and pronounced acquisition of new information. This dissertation sought to examine the relationship between daytime napping and memory consolidation in preschool-aged children during this transitional time. Children were taught either a declarative or an emotional task in the morning, and memory was probed following a nap and following an equivalent period of wake. Memory was also examined 24-hours later in the morning after overnight sleep. Overall, memory for both declarative and emotional information was shown to benefit from the nap. In both experiments, napping protected encoded information, whereas wake-promotion during the day led to an approximate 10% reduction in memory accuracy the following morning. Performance on the declarative memory task was associated with sleep spindles in the nap, whereas performance on the emotional memory task was related to nap slow wave activity. The results of this dissertation indicate that napping is important for memory consolidation of newly learned information in preschool-aged children. As such, this work supports the continued practice of nap promotion in preschool classrooms.