This paper proposes a re-conceptualization of firm internationalization to understand and predict the rapid global expansion of firms since the 1990s, especially those from emerging markets. First, based on a review of existing literature, we re-conceptualize firm internationalization as a heterogeneous process of strategic development of subsidiaries in overseas countries or regions. This re-conceptualization captures the pluralistic character of the process of firm internationalization.Second, we delineate peculiar roles played by subsidiaries in pursuit of multinational enterprise (MNE) headquarters' internationalization strategies. We argue that the HQ's heterogeneous strategies toward overseas subsidiary development define the corresponding roles of subsidiaries, which in turn shape the knowledge-flow patterns within the MNEs. Finally, we link firms' internationalization strategies with different subsidiary roles to generate hypotheses concerning the effect of such links on subsidiary performance. We argue that the proper alignment of HQ's internationalization strategies with subsidiary roles will lead to success of the overseas subsidiaries; by contrast, a mismatch will lead to subsidiary failure. The paper thus contributes to the field of firm internationalization by linking its new conceptualization with the literature on subsidiary roles and knowledge flows in MNEs.