Hydrothermal fault-related dolostones are common in extensional basins worldwide. Here, we present a diagenetic study of the dolostone bodies present in the early Aptian Villarroya de los Pinares Formation in the western marginal depocentre of the Maestrat Basin, named the Galve Sub-basin. Mapping of dolostone bodies was performed with the assistance of drone imagery. Fifty samples of limestones, dolostones and veins were collected for their petrological (optical, cathodoluminescence, and electronic microscopes) and geochemical characterization (δ18O and δ13C). Dolomitization is related to Mesozoic fractures, which acted as paths for dolomitizing fluids together with grainy limestone facies. On the other hand, micrite-rich beds acted as barriers, forcing the development of stratabound bodies. Three main diagenetic stages (early, burial and telogenesis) are recognized affecting the early Aptian limestones of the Villarroya de los Pinares Formation. Early diagenesis is defined by micritization, aragonite dissolution, and calcite cement CC1, with δ18O around -6‰VPDB and δ13C around +4‰VPDB, suggesting precipitation from slightly evolved marine waters. Burial diagenesis is represented by replacive dolostones RD1 and RD2, saddle dolomite SD1 and calcite cements CC2 and CC3. RD1, RD2, and SD1 show similar isotopic values (δ18O between −7.7 and −5.6‰VPDB and δ13C between −1.2 and +5.1‰VPDB), suggesting a single but continuous dolomitization event caused by hydrothermal brines. Calcite cements CC2 and CC3 postdate SD1 and have δ18O between −12.7 and −10.8‰VPDB and δ13C between −7.2 and −3.2‰VPDB indicating precipitation from high-temperature formation waters. Finally, late calcite cement CC4 and local calcitization of dolostones, with δ18O between -9.7 and −7.1‰VPDB and δ13C between −5.5 and −2.6‰VPDB, indicate the input of low-temperature meteoric fluids caused by the uplift related to the Alpine Orogeny. A similar diagenetic evolution has been reported in hydrothermal fault-related dolostones at the eastern margin of the Maestrat Basin (Orpesa and Morella sub-basins). Further integration is required in order to fully characterize the late Cretaceous hydrothermal event responsible for these dolomitizations at a basin scale.