Pursuit of international markets and resources from foreign sources has increased dramatically across the globe during the past three decades, and the academic study of international diversification has increased concurrently. Although scholars have studied several areas of international diversification research, there are still some unsolved problems, and new theoretical perspectives are needed to advance the field. In this thesis, I derive comprehensive models of international diversification by examining these variables through new perspectives. Based on positive organisational scholarship, configurational and institutional perspectives, I build new theoretical frameworks to fill gaps in international diversification research. This dissertation comprises three studies. Each of the studies examines different angles of international diversification, and the three individual research papers are intertwined to provide a coherent and integrated framework for this thesis. In Study 1, I elaborate a theoretical framework advancing the generalisation of international diversification research in emerging economies. Previous studies mainly focus on international diversification of multinational enterprises (MNEs) from well-developed countries, but largely ignored international diversification of emerging economy MNEs. To fill this research gap, Study 1 captures how Top Management Teams' (TMT) industrial and institutional factors influence mixed foreign direct investment (FDI), an important type of international diversification especially for emerging economy firms. Following the positive organisational scholarship perspective, I examine the positive influence of TMT functional diversity on emerging economy firms' likelihood of conducting mixed FDI. Furthermore, the effect of TMT functional diversity on mixed FDI is contingent on the social context of the TMT, competitive condition of the industry, and institutional development of firm locality. As an extension to Study 1, Study 2 evaluates the impact of various international diversification strategies on firms' internationalisation performance in the context of emerging economies. Within the configurational perspective, Study 2 investigates equifinal paths for emerging economy firms to achieve strategic fit (in the form of desired internationalisation performance) through configurations of the TMT's structure, international diversification strategy, and environmental condition. Within fuzzy-set analysis, the empirical results support my proposition about configurations of strategic fit in an emerging economy firm's international diversification, and multiple equifinal strategic-fit paths have been found. In Study 3, I extend the literature by developing arguments for performance benefits of institutional diversification strategies of MNEs. Existing studies have largely overlooked host-country institutional differences when considering the effects of different foreign countries on the MNE performance. I seek to fill this research gap by teasing out the effects of institutional diversification, and building theory on the relationship between different types of institutional diversification and MNE performance. Based on new institutional economics and comparative institutionalism, I divide institutional diversification into two main types: vertical institutional diversification and horizontal institutional diversification. I propose that the degree of vertical institutional diversification will have a negative effect on the MNE performance, while the scope of this diversification will serve to strengthen this negative effect. For horizontal institutional diversification, I propose that the MNE's degree of this diversification will have a positive effect on its performance, and its scope weakens this positive effect.