Drawing from Lent and Lopez’s (2002) “tripartite” model of relational efficacy, the overall purpose of this study was to examine antecedents and consequences of self-effcacy, other-efficacy, and relation-inferred self-efficacy (RISE) within six international-level athlete dyads. Semistructured interviews were conducted and data were content analyzed using deductive and inductive procedures. Sources of efficacy emerged in relation to perceptions regarding (i) oneself, (ii) one’s partner, (iii) the dyad/relationship, and (iv) external factors. Results also revealed the emergence of a number of salient intrapersonal and interpersonal outcomes, incorporating cognitive, affective, as well as behavioral consequences. Implications for theory development and future research are considered, and applied propositions are discussed with regard to effective relationship management in elite sport.