This study asked whether children's tendency to imitate selectively (ignore causally unnecessary actions) versus faithfully ("overimitate" causally unnecessary actions) varies across ages and social contexts. In the first experiment, 2-year-olds and 4-year-olds were randomly assigned to play 1 of 3 prior games with a demonstrator: a mimicry game, an instrumental game, or a noninteractive control game. They then participated in a puzzle-box imitation task in which the demonstrator performed 1 causally necessary and 1 unnecessary action to retrieve an object. Whereas 4-year-olds imitated faithfully across all conditions, 2-year-olds were more likely to imitate faithfully after a mimicry game and to imitate selectively after an instrumental game. Experiment 2 showed no effect of playing a mimicry game with a different experimenter prior to the imitation trials, thus ruling out 2-year-olds' faithful imitation being the result of motor priming or training effects. The results are discussed in terms of children's social affiliation and social-cognitive inferences.