Tungsten Carbide-20 weight % Cobalt (WC-20 wt% Co) coatings were extensively used material to achieve a combina-tion of extreme hardness and excellent strength. Hence, an effort has been made to improve the toughening properties of WC-Co coatings through reinforcement of Carbon Nano-Tubes (CNTs) using High-Velocity Oxy-Fuel (HVOF) spraying process. In this work, 2 wt%, 4 wt%, and 6 wt% of CNTs were blended by the ball milling process with WC-Co powders. These composed powders were deposited by HVOF process on to the plain mild steel substrates. The scratch test analysis on as-sprayed coatings showed that due to the addition of CNTs on WC-Co coatings, the resistance to penetrate the coating surface increased. Also, by varying the percentage of CNTs in the coating system, the pores were reduced. This phenom-enon is attributed to the toughening mechanism by forming a CNT bridge which avoids the formation of internal cracks. © 2020, Informatics Publishing Limited & Indian Society for Surface Science and Technology. All rights reserved.