A 2-year field study was conducted in central Greece (Larissa) and was repeated simultaneously in northern Greece (Thessaloniki) to determine the productivity and the competitive ability against corn poppy (Papaver rhoeas L.) of six faba bean (Vicia faba L.)-barley (Hordeum vulgare L.) intercrops grown at three seeding ratios (75:25, 50:50 or 25:75% of the recommended seeding rates) and two crop arrangements (alternate or mixed rows). Faba bean and barley sole crops were also included. Corn poppy dry weights in barley sole crop or faba bean-barley intercrops were 83 to 85% or 50 to 99%, respectively, lower than that in faba bean sole crop. Total dry matter (DM) and total crude protein (CP) yields of faba bean-barley intercrops were, in most cases, not significantly affected by corn poppy competition. The results obtained in both locations indicated that intercropping faba bean with barley could be an alternative practice to that of faba bean sole crop in sustainable production systems, because of its greater productivity, balanced nutritive value and competitiveness against aggressive weeds such as corn poppy.