Competitive loss can affect sport teams at both individual and collective levels because athletes’ emotional responses are shaped through interpersonal interaction and the wider emotional climate of the group. Following defeat, athletes may experience disappointment, frustration, anger, sadness, embarrassment, or reduced confidence, while teammates simultaneously observe, interpret, and respond to one another’s emotional reactions. This article examines collective emotion regulation after team-based competitive losses from sport and social psychology perspectives. The conceptual framework integrates emotion-regulation theory, interpersonal emotion regulation, emotional contagion, social identity theory, appraisal perspectives, collective efficacy, team cohesion, social support, and team resilience. Existing research indicates that emotional experiences in team sport are socially embedded and may be influenced by teammate relationships, leadership, group norms, shared identity, and communal coping. Because no original participant-level dataset was available, all quantitative values are explicitly simulated. Illustrative collective emotion-regulation scores of 2.62, 3.61, and 4.49 represent low, moderate, and high teammate-support conditions, while simulated contribution indicators of 46%, 41%, and 36% represent teammate social support, shared team identity, and collective coping. These values are methodological illustrations rather than empirical estimates. The conceptual analysis distinguishes individual, interpersonal, and collective emotion regulation and proposes four stages: appraisal of the loss, interpersonal emotional transmission, coordinated regulation, and collective recovery. Supportive communication, constructive feedback, realistic reappraisal, and perspective-taking may facilitate recovery, whereas blame, withdrawal, hostile communication, suppression, and rumination may prolong emotional disruption. Future research should use longitudinal, experience-sampling, multilevel, and observational designs to examine how collective emotion regulation influences cohesion, efficacy, resilience, motivation, and subsequent performance.