Nanocrystalline Sn(1−x)CoxO2 (x = 0, 0.01, 0.03 and 0.05) nanoparticles have been synthesized under microwave irradiation using oxalic acid (H2C2O4) as reducing agent. X-ray diffraction studies show that the prepared nanoparticles are crystalline with tetragonal crystal system and with few additional phases, which is further supported by Raman spectroscopy. The variation in molar concentration of Co2+ ions had a significant effect on size and morphological aspects which is evident from high resolution microscopic images. The emission owing to band edge position, recombination with Vo ++ centers and recombination with shallow level defects were observed from the Photoluminescence spectrum. The existence of room temperature ferromagnetism has been clearly observed using magnetization hysteresis measurements and the magnetic moments are found to decrease with the increased cobalt ions concentration. The decrease in charge carriers that arises due to the formed impurity phases and its significant effect on electron transfer capability have been discussed with the assistance of cyclic voltammetry. This study possibly will bring better insight for understanding the effects of doping concentration, formation of impurity phases and explicate the consequences of them on various properties of nanostructured materials. © 2016, Springer Science+Business Media New York.