Sr isotope records from marginal marine basins track the mixing between seawater and local continental runoff, potentially recording the effects of sea level, tectonic, and climate forcing in marine fossils and sediments. Sr/ 86 Sr analyses from the astronomically tuned Lower Evaporites in the central Apennines (Italy) allow us to explore the effect of glacio-eustatic sea level and precipitation changes on 87 Sr/ 86 Sr. Most variation in our data can be explained by changes in sea level, with greatest negative excursions from global seawater values occurring during relative sea level lowstands, which generally coincided with arid conditions in the Mediterranean realm. We suggest that this greater sensitivity to lowered sea level compared with higher runoff could relate to the inverse relationship between Sr concentration and river discharge. Variations in the residence time of groundwater within the karst terrain of the circum-Mediterranean region during arid and wet phases may help to explain the single (robust) occurrence of a negative excursion during a sea level highstand, but this explanation remains speculative without more detailed paleoclimatic data for the region.