We have investigated in detail properties of hybrid polyelectrolyte-anion exchange membranes (AEMs) having different amounts of a guanidinium-modified poly(allylamine hydrochloride) (PAH-Gu) derivative (2, 5, and 8 wt%). The presence of guanidinium groups at the membrane surface was confirmed by XPS. For 2 and 5 wt% the blended membranes are homogeneous, while at 8 wt% segregation is observed by AFM. The membrane permselectivity and ionic electrical resistance for phosphate reduce upon incorporation of the PAH-Gu in the membrane, reflecting an increased co-ion (H+ and Na+) permeation. We conclude that PAH-Gu loaded in the AEM favors an interaction with phosphate. In electrodialysis, using sodium sulfate and sodium dihydrogen phosphate at equal concentrations in the source phase a slight preference for phosphate was observed. Our work shows that this facile membrane fabrication procedure shows great potential in terms of tuning the membrane properties. One way to boost selective ion transport could be by increasing the number of functional groups in the membrane.