This article examines how perceiving concealment in close relationships influences marital well-being. It suggests that the perception of concealment from a partner signals separateness from one's partner and contributes to feelings of perceived partner exclusion. These feelings of exclusion, in turn, should negatively affect relational quality. These predictions are tested in a prospective study among 199 newlywed couples. Results suggest that perceiving concealment reduced marital adjustment and trust and increased conflict over time. Importantly, change in perceived partner exclusion mediated these effects. This article demonstrates that the perception of concealment (a) has deleterious effects on relational well-being in the long run and (b) is harmful in part because it elicits feelings of exclusion. © 2009 by the Society for Personality and Social Psychology, Inc.