This paper presents an interbehavioral conceptualization of interpersonal relationships, emphasizing both interpersonal closeness and conflict. In doing so, processes of association and subsequent substitution of stimulus function are described, setting the foundation for an analysis of how relationships are formed from an interbehavioral perspective. Specific attention is given to factors that impact intimacy and closeness in relationships, especially ways in which closeness may be fostered and conflict made more likely. The topic of communication is addressed, and possible therapeutic targets are highlighted from a novel conceptual context. The analysis is contrasted with more traditional ways of thinking, including more common behavior analytic perspectives. The implications of adopting the proposed interbehavioral conceptualization are provided.