Children's ability to understand and infer the thoughts and feelings of others influences how they develop a unique view of the world. Examining developmental factors that impact young children's success in both social and cognitive domains has important implications for advancing our current knowledge of social cognition. The purpose of this study was to examine relations among emotion knowledge, deception detection, and Theory of Mind to shed light on the development of social cognition. Specifically, preschoolers' deception detection skills were found to moderate the relationship between emotion knowledge and Theory of Mind. Thus, children's ability to use their emotion knowledge to understand the points of view of others varies as a function of their ability to detect deception. Implications for child development are discussed.