Over a period of 18 months, we studied the life history of Etheostoma fusiforme barratti, the southern subspecies of the Swamp Darter, in Hatchet Creek in the Suwannee River drainage of Florida. We found E. f. barratti on sandy and muddy substrates with dense vegetation and woody debris. Field data suggested a lifespan of up to 14 months, although individuals survived 18 months in an aquarium. There was no significant difference between the mean standard lengths of males and females, and the sex ratio was 1:1. The largest specimen collected was a 50-mm SL (59-mm TL) reproductively mature male. Midge larvae (Chironomidae) and water fleas (Cladocera) were the most common food items. Individuals in the smallest size class, 10–19 mm SL, consumed a larger proportion of small food items such as cladocerans and midge larvae, and larger Swamp Darters ate larger food items such as caddisflies, and consumed a larger variety of food items. Approximately one-third of all E. f. barratti dissected were parasitized by a digenean trematode. A large increase in the female gonadosomatic index occurred in January in each of the 2 study years as the darters approached 1 year of age and were at least 25 mm SL. Spawning occurred in January–May 2016 and January–April 2017. In an aquarium, adhesive eggs were attached to aquatic plants by females and fertilized by males. Numbers of mature and maturing ova were extremely variable (4–226), suggesting that E. f. barratti is a batch spawner and lays eggs over several mating bouts rather than during a single spawn. Compared to the northern subspecies, E. f. fusiforme, E. f. barratti reaches a larger size, 59 vs. 55 mm TL, and spawns earlier and longer, from January to April vs. April to May. Males of E. f. barratti, but not of E. f. fusiforme, were aggressive and possibly territorial during spawning. Etheostoma f. barratti may have a shorter life span, 14–18 months, compared to 2 years in E. f. fusiforme. This study provides baseline life-history data for a widespread and common species that has the potential to affect the structure and function of aquatic ecosystems.