Pleasant Bay, MA, is a coastal lagoon system featuring diverse habitats that support a variety of commercially, recreationally, and ecologically important marine species. In response to ecosystem changes noted by natural resource managers, we conducted an inventory of commercially and recreationally important shellfish and finfish in the bay from 2014 to 2017, the first such survey to be conducted since 1966. Fish and macroinvertebrate community composition and seasonal patterns of abundance during this study were broadly similar to those observed during other recent studies along the eastern shore of Cape Cod. This comprehensive inventory indicated that Pleasant Bay is home to a diverse and changing assemblage of marine species, some of which utilize the bay as spawning or nursery habitat. Long-term monitoring is necessary to place our observations in the broader contexts of short-term variability and long-term change.