Changes in the biosphere require ecological baselines in order to compare past, present, and future conditions and identify their effects. Establishing ecological baselines for infauna in southeastern Florida is a key component to understanding effects of current and future disturbances; however, nearshore sediment infaunal communities are neither as thoroughly investigated nor as well understood as, for example, coral reefs, seagrass beds, and mangroves. Baseline studies help assess and monitor changes due, for example, to human population growth, sea level change, and global warming. Therefore, six benthic cores were collected quarterly from six locations from May 2015 to February 2016 using a 7.7-cm PVC corer to examine macroinfaunal composition, richness and diversity in relation to environment, month, and sediment characteristics (e.g., composition and sphericity). Results suggest a latitudinal gradient of infaunal abundance and diversity, which was negatively correlated with median grain size. The middle sites located nearer the Florida Current and adjacent to the extensive carbonate deep ridge complex recorded higher percentages of carbonate and median grain size than the northernmost and southernmost sites. The dominant fauna included polychaetes (chiefly Armandia agilis, Paraonis fulgens, and Leitoscoloplos fragilis), isopods (Eurydice piperata and Ancinus depressus), and mysid shrimp (Chlamydopleon dissimile). Polychaetes dominated most samples and sites; however, peracarid crustaceans (chiefly isopods) dominated three sites in May and four sites in February samples. The recency of beach replenishments showed no long term effects on the infauna. This study provides an initial baseline that will permit comparison with future macroinfaunal and sediment studies along the southeastern Florida coast.