In classic examinations of the representativeness heuristic, Kahneman and Tversky (1973) presented adult participants with a description of an individual who fit their stereotype of a typical engineer. Importantly, even when participants were told that the individual was drawn from a sample of 70 lawyers and 30 engineers, they estimated that the individual was an engineer at very high levels, showing that they relied almost exclusively on the personality description. Relying on the representativeness heuristic can lead to base-rate neglect and, thus, biased judgments. Two experiments provide insight into the development of the representativeness heuristic in young children using an adaptation of the classic lawyer–engineer problem. Experiment 1 (N = 96) established that 3- to 5-year-olds can use base-rate information on its own, and 4- and 5-year-olds can use individuating information on its own, to make inferences. Experiment 2 (N = 192) varied the relevance of the individuating information across conditions to assess the pervasiveness of this bias early in development. Here 5- and 6-year-olds, much like adults, continue to attempt to rely on individuating information when making classifications even if that information is irrelevant. Together, these experiments reveal how the representativeness heuristic develops across the preschool years and suggest that the bias may strengthen between 4 and 6 years of age.