For the development of humidity sensors, MWCNTs/Co3O4 nanocomposite has been prepared by precipitation method. in order to evaluate the prepared materials quality both of functionalized MWCNTs and decorated CNTs characterized by X- ray powder diffraction (XRD) ,High resolution transmission electron microscope (HRTEM) Thermal analysis (DTA and TGA) FTIR and finally Raman spectroscopy. Meanwhile the humidity sensing behavior has been also investigated. The proposed composite has been tested in the wide range in relative humidity and tesing frequency. The obtained results confirmed that the optimum testing frequency is 100 Hz. The MWCNTs/Co3O4 nanocomposite exhibited a good sensitivity toward humidity from11% up to 97% RH with reasonable response and recovery time. Also the sensor revealed a low hysteresis and good repeatability with increasing and decreasing of humidity levels.