We aimed to examine cross-sectional and longitudinal relationships between psychological characteristics, body size, and body image outcomes in 6- to 7-year-old children. Participants were 202 children (91 boys, 111 girls) assessed when 6 and 7 years old. Body image-related variables, body mass index, and psychological characteristics were assessed. Cross-sectionally in the total sample, lower self-esteem was associated with greater body dissatisfaction, internalization of appearance ideals, and rewards of muscularity. Greater perfectionism was associated with greater body dissatisfaction, dietary restraint, drive for muscularity, and rewards of thinness and muscularity. Prospectively, internalization and socially prescribed perfectionism at 6 predicted greater body dissatisfaction at 7; higher perfectionism predicted greater rewards of thinness; higher perfectionism and lower self-esteem predicted greater rewards of muscularity; and lower self-esteem and smaller perceived body size predicted higher internalization. Exploratory gender specific analyses suggest that self-esteem may play a greater role in the development of body image attitudes in girls than boys, while perfectionism appears to increase boys' vulnerability to perceive greater rewards from thinness. Findings support the inclusion of psychological characteristics in etiological models of early body image development, and highlight perfectionism, internalization of appearance ideals, and self-esteem as potential targets for preventative interventions in this age group.