This chapter focuses on the ways that relational uncertainty can both shape and reflect relationship maintenance behaviors. Relational uncertainty reflects questions about the nature or degree of involvement in close relationships. Relational uncertainty can shape relationship maintenance because, under these conditions, people lack a sufficient framework to guide their own behavior or properly interpret the actions of a partner, which could prevent people from taking actions to maintain or bolster the relationship. When people fail to enact relationship maintenance, the interpersonal climate in the relationship can also give rise to increased questions and uncertainty about relational involvement. This chapter begins by reviewing the different types of uncertainty that can exist in close relationships and describes theory that explicates the role of uncertainty in interpersonal relations. Then, the chapter discusses the ways in which relational uncertainty can be an antecedent to relationship maintenance or an outcome of relationships that are not sufficiently maintained. Finally, the chapter concludes by exploring opportunities for future research on relational uncertainty and relationship maintenance.