The aim of this research is to investigate the effect of various coke sizes on the properties of carburized mild steels; therefore, five sets of samples were prepared and carburized at different temperatures and times. Three sets were carburized at 850, 900 and 950 °C for 120 min, while two other sets are carburized at 1000 and 1050 °C for 120 min. All sets were carburized using three different sizes of coke, namely A (<0.4 mm), B (1:1.6 mm) and C (4:5 mm). After carburization, all sets were quenched in water and then tempered at 200 °C for 15 min. After tempering, different mild steel samples were subjected to microstructure observation, hardness test, Charpy impact test, tensile testing and adhesive wear test. The experimental results were analyzed and show that mild steels carburized at 1050 °C with intermediate coke grain size B (1-1.6 mm) give the optimum results for the mechanical and wear properties which may be due to the microstructure obtained at this temperature (martensitic case and bainitic core). This indicates that coke size B gives the optimum combination of surface area and porosity needed for the reaction kinetics, as well as the highest wear resistance after different carburizing temperatures. [ABSTRACT FROM AUTHOR]