The organization of knowledge according to relations between concepts is critically involved in many cognitive processes, including memory and reasoning. However, the role of learning in shaping knowledge organization has received little direct investigation. Therefore, the present study investigated whether informal learning experiences can drive rapid, substantial changes in knowledge organization in children by measuring the effects of a week-long Zoo summer camp versus a control camp on the degree to which 4- to 9-year-old children’s knowledge about animals was organized according to taxonomic relations. Although taxonomic organization did not differ at pre-test, only Zoo camp children showed increases in taxonomic organization at post-test. These findings provide novel evidence that informal, real-life learning experiences can drive rapid knowledge organization change.