Lupinus gredensis is recorded as a new species for the adventive flora of Bulgaria. It was discovered in the Eastern Rhodope Mountains (Ivaylovgrad and Krumovgrad districts). The species grows in open dry grasslands and roadside ruderal vegetation, on siliceous and serpentine substrates. Its most distinctive feature is the change of the flower color, which is cream to off-white at first, and subsequently, in the ageing flowers of the same inflorescence, turning lilac to mauve. Lupinus gredensis is an endemic taxon restricted to the Iberian Peninsula. So far, it has been known as an alien species only in Greece. Revisiting the available records of L. hispanicus from Turkey has revealed that they also belong to L. gredensis. In Bulgaria, the earliest finding of L. gredensis, erroneously identified as L. luteus, dates back to 2003. The aim of the present article is to report L. gredensis as an addition to the Bulgarian alien flora and to provide data on the main distinguishing characters of the species and its distribution in Bulgaria and Turkey.