This study examined the site fidelity, group size, and seasonality of dolphins (Tursiops truncatus) in the Atlantic Ocean along Florida's east-central coast, and evaluated dolphin movements between the coastal waters and the adjacent Indian River Lagoon Estuary (IRL). Dolphin sightings occurred in each month surveyed (2/2006–8/2008); of 221 photo-identified dolphins, 185 (83.7%) were seen ≤2 times. Low sighting frequencies suggest an extended geographic range beyond the 80 km latitudinal study area, or transience. Twenty-five dolphins seen during exploratory surveys (10/2002–10/2005) were re-sighted, indicating some level of longer-term residency for particular individuals. Increases in relative abundance in winter and spring indicate that at least some of the population may be migratory. Group size averaged 6.0 (SD = 7.8), and most frequently contained two individuals (22.8%). Calves were present in 88 of 167 (52.6%) groups encountered. Four dolphins that exhibited year-round site fidelity to the estuary were observed once in the ocean within 1 km of an inlet. One female and a dependent calf, which were first observed in the ocean, immigrated into the estuary. The limited movement between the coastal Atlantic and the IRL populations supports discrete management units, with low potential for disease transmission.