This manuscript reports on the structural, magnetic and electrical properties of Al-Cr co-substituted nickel ferrites; NiAlxCrxFe2-2xO4 (0.0 <= x <= 0.6), synthesized via oxalate decomposition route. The decomposition process was monitored using DTA-TG techniques, and the obtained ferrites were characterized using XRD, FT-IR, VSM, AC-magnetic susceptibility and electrical properties measurements. The single-phase structure was confirmed using XRD and FT-IR spectroscopic measurements. With increasing Al-Cr substitution, the obtained saturation magnetizations, via VSM measurements, showed a gradual decrease while coercivity exhibited a steady increase. The electrical properties as a function of temperature and frequency showed a semiconducting behavior with conductivity decreasing by increasing substitution, which enhances the use of these materials in microwave devices applications. (C) 2014 Elsevier Ltd. All rights reserved.