This paper theorizes the role of shared responsibility in the development of affective group attachments, interweaving ideas from social exchange and social identity theories. The main arguments are that (1) people engaged in task interaction experience positive or negative emotions from those interactions; (2) tasks that promote more sense of shared responsibility across members lead people to attribute their individual emotions to groups or organizations; and (3) group attributions of own emotions are the basis for stronger or weaker group attachments. The paper suggests that social categorization and structural interdependence promote group attachments by producing task interactions that have positive emotional effects on those involved.