Purpose: Given the essential role of theories in research, this study aims to identify the theories and concepts undergirding educational leadership research, illuminate the interconnections among them, and examine the evolution of the theoretical groundings of the field from 2005 to 2014. Methods: This study constructed a concept co-occurrence network, in which the nodes represent all the framing concepts that theoretically framed the 1,328 articles published in four leading educational leadership research journals ("Educational Administration Quarterly," "Journal of Educational Administration," "Educational Management Administration & Leadership," and "Journal of School Leadership") over the past decade and the ties link the concepts that co-occur in an article. The reference frequency and centrality measures were used to identify the influential concepts. Next, the k-core analysis was performed to visualize the interconnections among the concepts. Moreover, a series of network cohesion measures were used to detect the changes in conceptual cohesion over the past decade. Findings: While 295 framing concepts guided the educational leadership empirical studies, a small number of concepts exerted a disproportionately large influence on the research. Furthermore, these influential concepts closely interplay with one another, and the strongest interconnection was seen between the concepts of leadership approaches and organizational perspectives. Last, the increasingly pluralistic theoretical foundation did not yield the growing conceptual cohesion in educational leadership. Implications: This study for the first time elucidates the structure and evolution of the theoretical groundings of educational leadership research, laying the foundation for further theory development and inviting researchers to bring conceptual cohesion to this field through integrating concepts, allowing random ideas to mutate, and developing new theories.