Seagrass epiphyte blooms potentially have important economic and ecological consequences in Tampa Bay, one of the Gulf of Mexico`s largest estuaries. As part of a Tampa Bay pilot study to monitor the impact of environmental stresses, precise characterization of epiphyte diversity is required for efficient management of affected resources. Thus, epiphyte diversity may be used as a rational basis for assessment of ecosystem health. In May 2001, epiphytic species encompassing green, brown and red macroalgae were manually collected from dense and sparse seagrass beds of Thalassia testudinum and Syringodium filiforme. A total of 20 macroalgal epiphytes, 2 Chlorophyta, 2 Phaeophyta, and 16 Rhodophyta, were found on T. testudinum and S. filiforme seagrass at the four sampling sites (Bishop Harbor, Cockroach Bay, Feather Sound, and Mariposa Key). The Rhodophyta, represented by 16 species, dominated the numbers of species. Among them, the thin-crusted Hydrolithon farinosum was the most commonly found epiphyte on seagrass leaves. Species number, as well as species frequency of epiphytes, is higher at dense seagrass sites than sparse seagrass sites. Four attachment patterns of epiphytes can be classified according to cortex and rhizoid development: 1) creeping, 2) erect, 3) creeping & erect, and 4) erect & holding. The creeping type is characterized by an encrusting thallus without a rhizoid or holdfast base. Characteristics of the erect type include a filamentous thallus with or without a cortex, and a rhizoid or holdfast base. The creeping and erect type is characterized by a filamentous thallus with a cortex and rhizoid. A filamentous thallus with a cortex, holdfast base, and host holding branch is characteristics of the erect and holdfast attachment type. This study characterized each species found on the seagrass for epiphyte identification.