Seagrass meadows are under threat from a range of anthropogenic disturbances, including the impacts of habitat loss, eutrophication and overfishing. These threats modify the functioning and structure of seagrass ecosystems by reducing the diversity of species that deliver key ecological functions within seagrass meadows linked to the ecosystem’s resilience. Fish are a crucial component of seagrass food webs, and support important ecological functions including carnivory and herbivory, which are essential for transferring energy throughout the food web. Here, we aim to investigate how the functional diversity of fish relates to multiple ecological functions within seagrass meadow ecosystems. We surveyed fish communities using baited and unbaited underwater video systems and multiple ecological functions across the seagrass meadows of Moreton Bay, Queensland, including carnivory, herbivory and the diversity and cover of seagrass. We found that fish was significantly correlated with carnivory functioning and the composition of the seagrass meadow, however, herbivory was found to respond positively with functional diversity initially, before plateauing as functional diversity continued to increase. These findings demonstrate the importance of a functionally diverse food web for functioning seagrass meadows and when conserving functioning seagrass meadows in the future, understanding the fish and seagrass composition is critical.