This paper offers a theory linking choice processes with the experience of transitory emotion and the development of enduring affective attachments to nested collectivities, i.e., subgroups within a larger group, organization, or society. According to the theory, persons become emotionally attached to groups that strengthen their generalized sense of control. The underlying propositions are that: (1) choice processes that foster a high sense of control produce positive emotion (happiness, pride, gratitude); (2) such positive emotion strengthens affective attachments to groups perceived as most responsible for the choice opportunity; and (3) such positive emotion strengthens attachments to proximal subgroups more than to larger, more encompassing collectivities. Complementary predictions obtain for lack of choice, negative emotion (sadness, shame, hostility), and the weakening of collective attachments. The theory explicates a subtle social process important to individual/group relations, and suggests conditions likely to produce behavior directed at the collective welfare.