This work concerns the investigation of ion transport behaviour of NaI containing lithium tungsten phosphate glasses in order to understand better the role of NaI in the ionic cation transport. Glasses obtained in the system 0.5[x(2NaI)-(1-x)Li2O]-0.5[0.25(WO3)2-0.75P2O5] were investigated. The glass samples have been characterised using powder X-ray diffraction (XRD), thermal analysis, density and impedance spectroscopy. X-ray diffraction and thermal studies have confirmed that these glasses can be formed in the range x = 0 to 1. The mixed alkali glasses have shown higher activation energies and lower conductivities compared to single alkali doped glasses and this has been attributed to a mixed alkali effect.