Amphipod crustaceans exist across marine habitats from the polar regions to the tropics, providing a critical biological link between benthic/pelagic processes and marine/atmospheric ecosystems. They fulfil many functional roles as predators and prey, bioturbators, mesograzers, pollinators, secondary producers, nutrient cycling facilitators, and indicators of marine and sediment health. Despite their importance, tropical amphipods are poorly represented in the literature. This review offers an overview of the biological and ecological roles of amphipods globally. Amphipods face many pressures in the warming seas that will ultimately force acclimation, adaptation, or mortality, with potentially dire consequences for the processes they facilitate. We highlight the lack of data on tropical amphipods and argue an urgent need to identify their diversity, abundance, and functions underpinning resilience in ecosystems such as coral reefs, seagrass meadows, and mangroves. This improved understanding is necessary to predict and potentially mitigate cascading deleterious effects driven by a rapidly warming planet.