This study examined the effects of motivation and goal maintenance on 3- and 4-year-olds’ prospective memory (PM), as well as the relation between executive functioning (EF) and PM. Children sorted picture cards into two boxes (ongoing task), but sorted target cards into a third box (PM task). Motivation was manipulated such that half the children engaged in a highly interesting activity when they successfully sorted target cards, while the others did not. Goal maintenance was manipulated such that half the children received more target cards early in the ongoing task, while the remaining children received them later. Four-year-olds outperformed 3-year-olds on the PM task, and 3-year-olds sorted fewer target cards in the high-motivation condition than the low-motivation condition. Early exposure to target cards did not result in higher PM performance. EF predicted PM performance, controlling for age and language ability, and fully mediated the effect of age on PM performance.