We present the first neodymium isotope reconstruction of Mediterranean–Atlantic water exchange through the Moroccan (‘Rifian’) Corridor 8–5 Ma. This covers the late Miocene Messinian Salinity Crisis (MSC); a period when progressive tectonic restriction of the Mediterranean–Atlantic seaways resulted in extreme, basin-wide Mediterranean salinity fluctuations. The Rifian Corridor was one of these seaways and until now, relatively poor age constraints existed for the timing of Corridor closure, due to the impact of uplift and erosion on the sedimentary record. The bottom water Nd isotope record from the continuous Bou Regreg Valley succession in northwest Morocco allows us to explore corridor connectivity with the Atlantic. Data from the interior and Mediterranean edge of the Rifian Corridor (respectively, the Taza–Guercif and Melilla basins, northern Morocco) provide new information on corridor shallowing and the provenance of water flowing through the seaway. As a result, we can constrain the age of Rifian Corridor closure to 6.64–6.44 Ma. We also find no evidence of the siphoning of Atlantic waters through the seaway (7.20–6.58 Ma). Our results cannot exclude the possibility that at times during the Messinian Salinity Crisis, Mediterranean Outflow Water reached the Atlantic.