The proto‐Paratethys Sea covered a vast area extending from the MediterraneanTethys to the Tarim Basin in western China during Cretaceous and early Paleogene.Climate modelling and proxy studies suggest that Asian aridification has been governedby westerly moisture modulated by fluctuations of the proto‐Paratethys Sea.Transgressive and regressive episodes of the proto‐Paratethys Sea have been previouslyrecognized but their timing, extent and depositional environments remainpoorly constrained. This hampers understanding of their driving mechanisms (tectonicand/or eustatic) and their contribution to Asian aridification. Here, we presenta new chronostratigraphic framework based on biostratigraphy and magnetostratigraphyas well as a detailed palaeoenvironmental analysis for the Paleogene proto‐Paratethys Sea incursions in the Tajik and Tarim basins. This enables us to identifythe major drivers of marine fluctuations and their potential consequences on Asianaridification. A major regional restriction event, marked by the exceptionally thick(≤ 400 m) shelf evaporites is assigned a Danian‐Selandian age (ca. 63–59 Ma) in theAertashi Formation. This is followed by the largest recorded proto‐Paratethys Sea incursion with a transgression estimated as early Thanetian (ca. 59–57 Ma) and a regressionwithin the Ypresian (ca. 53–52 Ma), both within the Qimugen Formation.The transgression of the next incursion in the Kalatar and Wulagen formations is nowconstrained as early Lutetian (ca. 47–46 Ma), whereas its regression in the BashibulakeFormation is constrained as late Lutetian (ca. 41 Ma) and is associated with a drasticincrease in both tectonic subsidence and basin infilling. The age of the final and leastpronounced sea incursion restricted to the westernmost margin of the Tarim Basin isassigned as Bartonian–Priabonian (ca. 39.7–36.7 Ma). We interpret the long‐termwestward retreat of the proto‐Paratethys Sea starting at ca. 41 Ma to be associatedwith far‐field tectonic effects of the Indo‐Asia collision and Pamir/Tibetan plateauuplift. Short‐term eustatic sea level transgressions are superimposed on this longtermregression and seem coeval with the transgression events in the other northernPeri‐Tethyan sedimentary provinces for the 1st and 2nd sea incursions. However, the3rd sea incursion is interpreted as related to tectonism. The transgressive and regressiveintervals of the proto‐Paratethys Sea correlate well with the reported humid andarid phases, respectively in the Qaidam and Xining basins, thus demonstrating therole of the proto‐Paratethys Sea as an important moisture source for the Asian interiorand its regression as a contributor to Asian aridification