Long-term ecological time series research provides a unique perspective on environmental processes, population dynamics, and emergent properties of ecosystems. The Narragansett Bay Long-Term Plankton Time Series is one of the world’s longest-running plankton surveys. Beginning in 1957, weekly samples have been collected to assess the phytoplankton community and characterize the physical parameters of Narragansett Bay. With over 60 years of data, we use this dataset to identify long-term changes in plankton community composition and abundance as well as shifts in phenology (i.e., annually occurring life history events). These observations in nutrient and phytoplankton dynamics have important implications for food web interactions in the region. The time-series dataset is publicly available here.