The current study extends the Broaden & Build theory of positive emotions to the collective level of analysis, focusing on the mediating role of group social resources (i.e. cohesion, coordination, teamwork, supportive team climate) between group positive affect (i.e. enthusiasm, optimism, satisfaction, comfort) and group performance (i.e. in-and extra-role performance, creative performance). To test our hypotheses, we conducted two studies using independent samples. Study 1 is a laboratory study with 449 participants nested in 112 small groups who performed an organizational simulation creative task. Study 2 is a field study that aggregated scores of 2159 employees nested in 417 groups. In both the lab and field studies, structural equation modeling results revealed that group social resources fully mediate the relationship between group positive emotions and performance (download article).