The Piacenzian (Late Pliocene) represents a natural laboratory within which frequency and magnitude of environmental changes during a period of past global warmth can be analyzed, climate models can be tested, and results can be placed in a context to better prepare for future change. We focus on the North Atlantic and both generate new and incorporate existing faunal assemblage and alkenone data from DSDP Sites 552 and 606, ODP Sites 662, 981, 982, and 999, and IODP Sites 1307, 1308 and 1313. In addition, cores and outcrop material containing Piacenzian sediments from the Atlantic Coastal Plain of Virginia, USA, are included. These data allow us to characterize regional changes in temperature, salinity, upwelling, productivity, and diversity, associated with climate transitions, and make nuanced reconstructions of mid-Piacenzian conditions within a high-resolution temporal framework between ~3.40 and ~3.15 Ma, inclusive of Marine Isotope Stages M2 through KM5. Our results indicate the slope of the North Atlantic sea surface temperature gradient is a robust feature of the Late Pliocene and we confirm a temperature anomaly (Pliocene minus pre-industrial) little to no change at the equator to >6° C near 60° North, during Marine Isotope Stage (MIS) KM5c (3.21 Ma – 3.20 Ma). The M2-M1 transition is accompanied by warming, rapid sea-level rise, reorganization of planktonic foraminifer assemblages, decreases in productivity and increase in zooplankton diversity. Abundance changes in stenohaline taxa document repeated freshening of the Caribbean by low latitude Pacific water associated with brief re-openings of the Central American Seaway. The Gulf Stream – North Atlantic Drift migrated to a more northerly position during both the M2-M1 and KM6-KM5 transitions. Preliminary comparison of these results to climate simulations produced by the second phase of the Pliocene Model Inter-comparison Project (PlioMIP2) indicates model output and reconstructed environmental data are in closer agreement than previous data-model comparisons. We attribute this to a combination of improved Pliocene Research, Interpretation and Synoptic Mapping (PRISM4) boundary conditions, and the refined stratigraphic window used for verification, compared to PRISM3.