<p>Boundaries are ubiquitous elements of daily consumption environments and range from visibly bounded product packaging to invisible boundaries such as brand extensions. However, only a few studies have explored the factors influencing consumers’ boundary preferences, and sufficient discussion, especially about the ways in which common environmental factors impact boundary preferences, is still lacking. This research investigates how and why consumers’ boundary preferences might be affected by social crowding. Across five studies, we find that consumers in crowded (vs. uncrowded) environments are more likely to seek boundaries, and this effect of social crowding is driven by consumers’ reduced sense of belonging. The influence of social crowding is also more salient for lonely (vs. not lonely) consumers. These findings offer meaningful insights for researchers and marketers who seek to better and more strategically utilize boundaries in various environments.</p>