Lake Maurepas, an oligohaline lake in southeastern Louisiana, USA, lies on the westernmost edge of the socio-ecologically important Lake Pontchartrain Basin. Relative to Lake Pontchartrain, our knowledge of the invertebrate community in Lake Maurepas is limited. We aim to establish a baseline dataset on the spatio-temporal variability of the invertebrate community within Lake Maurepas, including shrimp, blue crabs, Rangia clams, and other benthic macroinvertebrates. Our techniques include stratified-random crab trap setting to estimate abundance and measure the size of blue crabs, otter trawl pulling to investigate nekton community composition and petite PONAR grab dredging to assess benthic macroinvertebrate diversity. Our analyses for the first year indicate interesting spatial patterns in blue crab and Rangia clam densities, potentially influenced by three freshwater river inflows and one channel (in- and out-flow) connected to Lake Pontchartrain—the more brackish and estuarine component of the basin. We observed a temporal increase in the population of blue crabs and in the weight of Rangia clams, coinciding with increased water temperatures during the spring and summer. We also observe clear temporal patterns of invertebrate species abundance and community composition, driven by oligochaetes, midge larvae, and Probythinella mud snails. Freshwater shrimp populations remain relatively high, especially during the spring, while commercially important saltwater species are rarely collected despite their known tolerance for conditions similar to Lake Maurepas. Our data provide baseline information on the diversity and abundance of invertebrates in Lake Maurepas, which is important in light of future and ongoing anthropogenic impacts on the lake.