Chromium substituted Mn nanospinel ferrites having the formula MnCrxFe2-xO4 (0.0 a parts per thousand currency sign x a parts per thousand currency sign 1.0) have been synthesized using the microwave-assisted combustion synthesis. The composition, structural, spectroscopic features of the products were studied by X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. XRD investigations indicated the formation of single-phased cubic spinel structure for all products. Lattice parameters of the products represented the continuous decrease with increasing the substitution of Cr3+. The saturation magnetization of undoped sample appeared to be highest and as Cr3+ concentration increases magnetization of the samples decreases. There is one reflection loss minimum in all doped samples at around 13 GHz with magnitude of -12 dB mechanism of which is explained by quarter wave cancellation model.