This study investigated the effect of team-referent attributions on emotions and collective efficacy. A sample of 265 athletes, from 31 interdependent sport teams, completed measures of competition importance, the Sport Emotion Questionnaire (SEQ; Jones, Lane, Bray, Uphill, & Catlin, 2005), and a collective efficacy measure (CEM) immediately prior to competition. Immediately after competition, participants completed self-report measures of performance, the Causal Dimension Scale for Teams (Greenlees, Lane, Thelwell, Holder, & Hobson, 2005), the SEQ, and the CEM. Findings indicated that following team victory attributions of team control were associated with higher levels of postcompetition happiness. Further, an interaction effect for team control and stability demonstrated that if team victory was perceived as stable over time, a team controllable attribution was associated with higher levels of postcompetition collective efficacy. For losing teams, an interaction effect for external control and stability indicated that only when team defeat was not perceived as under the control of others would an unstable attribution favor collective efficacy. This study provides evidence that team-referent attributions contribute to emotions and collective efficacy beliefs in group achievement settings.