Although the role structure of top management teams (TMT) is a relevant topic in strategic leadership research, the hierarchical structure of TMTs still needs to be explored. In this study, we conduct an exploratory analysis to understand better how TMTs are hierarchically structured and what drives different hierarchical configurations across TMTs. Our empirical analysis of 260 Standard & Poor firms between 2007 and 2018 offers unique insights. Primarily, we discover that even though TMT sizes remained constant between the years of observation, they became less hierarchical in structure, meaning that TMTs became relatively flatter. Moreover, we find that several factors related to CEO characteristics, strategic leadership, corporate governance, and firm and environmental conditions drove the changes in the hierarchical structure of TMTs. These combined empirical insights call for nuanced theoretical explanations of TMT hierarchical structures. We contribute to the TMT literature mainly by highlighting the development of different TMT hierarchical structures and providing new insights into their determinants.