We conducted vessel-based line-transect sampling from December 2011 to November 2013 to quantify Tursiops truncatus (Bottlenose Dolphin) density over 8 consecutive seasons in the Mississippi Sound. Density estimates showed temporal variation ranging from 0.27 Dolphins/km² (CV% = 31.3) in spring 2013 to 1.12 Dolphins/km² (CV% = 21.6) in spring 2012. Density in winter and summer was stable compared to fall and spring, which fluctuated across years. We also noted spatial variation—density was commonly highest in the central and eastern portions of the Mississippi Sound. Spatial and temporal variation in temperature and salinity were potentially driving shifts in Bottlenose Dolphin density. Additional regularly collected density estimates using standardized protocols are needed in order to draw more definitive conclusions regarding the status and trend of this population.