Perceptions of the behavior of those around us provide important cues as to what our own behavior should be. However, we know relatively little about the source of these perceptions and how they develop in the course of interaction. This article provides a conceptual framework for the relationship between social network structure and perceptions of descriptive social norms—what other people in a group tend to do. Because networks represent (1) whom group members are exposed to, (2) the amount of exposure group members have to others, and (3) the type of exposure group members have to others, they shape individuals' perceptions of descriptive social norms. The article uses original data from a vegetarian co‐op on a university campus as an empirical example of how networks inform perceptions of norms in a group. The evidence demonstrates the utility of a network‐based approach to understanding the formation and change of social norms and the accuracy of perceptions of the behavior of others. I argue that the process by which individuals make inferences about group norms differs based on the type of behavior under consideration and the type of relationship between individuals.