The veracity of child witness testimony is central to the justice system where there are serious consequences for the child, the accused, and society. Thus, it is important to examine how children's lie-telling abilities develop and the factors that can influence their truthfulness. The current review examines children's lie-telling ability in relation to child witness testimony. Although research demonstrates that children develop the ability to lie at an early age, they also understand that lie-telling is morally unacceptable and do not condone most types of lies. Children's ability to lie effectively develops with age and is related to their increasing cognitive sophistication. However, even children's early lies can be difficult to detect. Greater lie elaboration requires greater skill and children's ability to lie effectively improves with development and as a function of cognitive skill. Different methods of promoting children's truthful reports as well as the social and motivational factors that affect children's honesty will be discussed.