This article examines developmental differences in children’s reasoning about secrecy and lying as well as their use of these behaviors in two studies. Study 1 explored children’s (N = 66, 8–15 years) reasoning about the circumstances in which secrecy and lying are acceptable. Study 2 analyzed children’s (N = 50, 8–15 years) actual reported daily frequency of secrets and lies in relation to maladaptive behavior problems. Overall, findings suggest that children’s motivations for secrecy and lying become more nuanced, and seemingly utilitarian, with age, and that children’s use of concealment may be an adaptive tool that facilitates social relationships.