Homogeneous chromium-multiwalled carbon nanotube (Cr-MWNT) composite coatings were electrodeposited from trivalent chromium [Cr(III)] electrolyte containing MWNTs under ultrasonic agitation. The microstructure, mechanical properties, and electrochemical corrosion behavior of Cr-MWNT composite coatings were investigated with a field-emission scanning electron microscope, an X-ray photoelectron spectrometer, a Vickers hardness indenter, and an electrochemical workstation. The introduction of MWNTs obviously improves the hardness and toughness of Cr coatings due to the "fiber reinforcement.'' Also, the electrochemical tests show that in H2SO4 solution MWNTs can provide a lot of active sites to accelerate the formation of Cr2O3 passive film, and in KOH solution they can adsorb Cr-n(OH)(x) polymer film to decrease the corrosion rate of Cr composite coatings.