When navigating unfamiliar social environments, it is important to identify who is powerful. Knowing who has power can be challenging because there may be limited social information available to an observer, and because people achieve influence for many reasons. In experiments with 3- to 5-year-old children (n = 192) and adults (n = 32), we investigated the developmental origins and conceptual structure of power judgments based on physical appearance. First, we examined participants’ judgments of strength and authority from facial structure and expansive body posture; next, we used a matching task to assess whether children thought that powerful faces and bodies “go together”. With age, children became increasingly sensitive to these two appearance cues and viewed both as evidence for both strength and authority. Unlike children, however, adults did not attribute strength to expansive body postures. Moreover, by 4 years, children brought facial and postural information together, indicating that they have formed a single, coherent representation of how they think powerful people appear. Overall, children’s sensitivity to postures preceded faces and their attributions of strength preceded authority, suggesting that an early capacity for assessing formidability may support later-emerging notions of power that are determined in a more normative manner.