Coral reefs, like all ecological systems, are a product of historical processes spanning extensive timescales. Hence, to fully grasp the complexities of present-day coral reef fish biodiversity, it is essential to delve into their evolutionary history. In this talk, I will demonstrate how historical insights can illuminate the assembly and functioning of contemporary coral reef fish faunas. Through three detailed case studies, I will explore the historical processes influencing fish ecologies, their interactions with corals, and with reefs more broadly. First, I will examine how historically warm temperatures may have played a role in the emergence and persistence of small-bodied, fast-growing fish species. Next, I will present research that prompts a re-evaluation of fish-coral interactions across both ancient and modern reef ecosystems. Finally, I will show how the rise of tropical marine fish faunas is intrinsically linked with the development of reefs in both space and time. These insights not only enhance our understanding of present-day coral reef biodiversity but also inform projections of their responses to ongoing environmental changes.