The National Institutes of Health has deemed illiteracy a national health crisis based on reading proficiency rates among American children. In 2002, the National Early Literacy Panel identified six pre-reading skills that are most crucial precursors to reading mastery and predict future reading outcomes. Of those skills, phonological awareness, and in particular phonemic awareness, is the strongest independent predictor of early reading outcomes. However, limited research has addressed the development of these component skills due in part to the fact that many of the measures used to assess sub-skills such as phonemic awareness are oral production measures that cannot easily be administered with children under the age of five, and are not designed to detect implicit or emerging knowledge. To address this limitation, we developed and administered two receptive measures of phonemic awareness to 2.5- and 3.5-year-old children. We found evidence for the emergence of this component skill earlier in ontogeny than is currently acknowledged in the literature. Overall, children performed at above chance rates on measures of receptive phonemic awareness at the level of the individual phoneme as early as 2.5-years-old. Results are discussed in terms of the need for a paradigm shift in prevailing models of how phonological awareness develops, as well as the potential to identify children at-risk for reading failure at an earlier point in ontogeny than is currently feasible.