The search for a continuous continental record of interglacial periods in semi-arid regions is problematic due to the absence of stable and continuous sedimentary systems over time in this type of climate. In this work, a relatively stable basin is described and analyzed during the last interglacial in a semi-arid region of the western Mediterranean. For this purpose a geomorphological, stratigraphic and sedimentological study has been carried out, with dating through 230Th. A semi-endorrheic Pleistocene basin has been identified, with two units that correspond to a fluvial-lacustrine system (unit P1) and an alluvial system (unit P2). Unit P1 has been dated in the MIS 5e interglacial episode. A framework is described in which the Aljezares Quaternary basin can be considered as a possible source of paleoenvironmental and paleoclimatic information in semi-arid regions from the last interglacial period in future studies.