Protandrena evansi Ruz and Chiappa n. sp. is described and illustrated. This new species was found at an aggregation of numerous individuals in a nesting site in Farellones, a locality of the Región Metropolitana in Central Chile, at 2612 m above sea level, visiting Senecio polygaloides Phil. (Asteraceae: Compositae), a plant endemic to the Andes. Some of its morphological features do not fit the diagnostic generic characters. Apical tergal hair bands have not been found before among the species of Protandrena s. l., including such subgenera as Metapsaenythia, Pterosarus, Heterosarus, Parasarus and Austropanurgus.