Diamond-Backed Terrapins (Malaclemys terrapin) are emydid turtles found in estuarine systems along the Gulf and Atlantic coasts of the United States between Texas and Massachusetts, and in Bermuda. Reductions in many terrapin populations have been documented throughout the species' range in association with habitat loss, overharvesting for consumption, bycatch in commercial and recreational fishing gear, and collection for the pet trade. Information on populations within Louisiana is limited, with survey efforts being performed only recently throughout the state's coastal zone. From 2012 through 2014, we sought to determine the distribution of Diamond-Backed Terrapins within the Deltaic Plain region of Louisiana, describe sex ratios and size class structure within select management basins, and establish marked populations to promote continued study of the species. Of the 27 terrapin sampling sites initially selected, 24 were chosen for further evaluation; a subset of these same locations were sampled more intensively in 2014. In all years, we utilized unbaited fyke nets. The presence of Diamond-Backed Terrapins was associated with a variety of coastal marsh vegetative communities (e.g., intermediate, brackish, and saline). Basin-specific analyses revealed variation in mean size, and sex ratios skewed toward males within all basins indicating higher female mortality rates or male-biased recruitment. These efforts confirm the presence of Diamond-Backed Terrapins across the Deltaic Plain region of the Louisiana coastline, and inform future examinations of the regional and range-wide abundance and population dynamics of the species.