Abstract: Three populations of Lasius jensi Seifert, 1982, a temporary social parasite, from two separate regions in Spain were detected. These locations represent the westernmost populations of the species. Lasius jensi is a new record for the Iberian Peninsula, bringing the total number of native ant species to 285. Dealate queens were captured with pitfall traps from mid July to mid August. Taking into account the other species present in the three populations, the host species could be Lasius alienus (FÖRSTER, 1850), Lasius grandis Forel, 1909 or Lasius piliferus Seifert, 1992. The zoogeographical significance of those populations, probably a relict from glacial refuge, is briefly discussed.