Poor social functioning is related to the development of psychosis; however, our current understanding of social functioning in those at-risk for psychosis is limited by (a) poor conceptual models of interpersonal behavior and (b) a reliance on comparisons to healthy controls (e.g., vs. clinical controls). In this study, we introduce Contemporary Integrated Interpersonal Theory (CIIT) and use its Interpersonal Circumplex (IPC) model to compare interpersonal behavior traits in those at clinical high-risk (CHR) for psychosis, clinical controls, and healthy controls. A community sample (N = 3460) was used to derive estimates of IPC dimensions (i.e., affiliation and dominance), which were then compared among a large subsample that completed diagnostic interviews (N = 337), which included a CHR group, as well as several control groups ranging on degree of psychosis vulnerability and internalizing disorders. CHR individuals were distinguished from healthy controls by low affiliation (d = -1.31), and from internalizing disorder groups by higher dominance (d = 0.64). Negative symptoms were consistently associated with low affiliation and low dominance, whereas positive symptoms were related primarily to coldness. These results connect social functioning in psychosis risk to a rich theoretical framework and suggest a potentially distinct interpersonal signature for CHR individuals. More broadly, this study suggests that CIIT and the IPC may have utility for informing diagnostics and treatment development in psychosis risk research.