Social hierarchies exist throughout the animal kingdom, including among humans. Our daily interactions inevitably reflect social dominance relationships between individuals. How do we mentally represent such concepts? Studies show that social dominance is represented as vertical space (i.e., high=dominant) by adults and preschool children, suggesting a space-dominance representational link in social cognition. However, little is known about its early development. Here, we present experimental evidence that 12- to 16-month-old infants expect agents presented in a higher spatial position to be more socially dominant than agents in a lower spatial position. After infants repeatedly watched the higher and lower agents being presented simultaneously, they looked longer at the screen when the lower agent subsequently outcompeted the higher agent in securing a reward object, suggesting that this outcome violated their higher-is-dominant expectation. We first manipulated agents’ positions by presenting them on a podium (Experiment 1). Then we presented the agents on a double-decker stand to make their spatial positions directly above or below each other (Experiment 2), and we replicated the results (Experiment 3). This research demonstrates that infants expect spatially higher-positioned agents to be socially dominant, suggesting deep roots of the space-dominance link in ontogeny.