We present three studies exploring 2- to 4-year-olds’ imitation on witnessing a model whose questionable tool use choices suggested her untrustworthiness. In Study 1, children observed the model accidentally select a physically optimal tool for a task and then intentionally reject it for one that was functionally nonaffordant. When asked to perform the task for her, children at all ages ignored the model’s intentional cues and selected the optimal tool. Study 2 found that when the model’s nonaffordant tool choice was emphasized by claims about its design, 3-year-olds increased imitation. They also imitated, as did 2-year-olds, when the model selected a suboptimal rather than nonaffordant tool. The 4-year-olds consistently avoided imitation. Study 3 replicated these findings with new tools and participants. Additional measures indicated that knowledge about artifact design predicted children’s tendency to ignore the model. These results shed light on developmental trends in the social and cognitive functions of imitation.