To investigate the effects of porous properties of supports on the methane decomposition of Co-Mo/MgO catalysts, supports having different porous properties were prepared by varying the synthesis temperature of MgO. Co-Mo/MgO catalysts were prepared using the impregnation method. The CM/4MgO catalyst using 4MgO support, which had the largest specific surface area of 170 m(2)/g, showed highest methane conversion of 85.7 % with 60.12 % of MWCNT production. The produced MWCNT on CM/4MgO had highest crystallinity and electrical conductivity with average diameter of 20.5 +/- 7.8 nm. Overall, the improved pore structure of MgO prepared by the oxidation process enhanced the dispersibility of the Co active metal, thereby improving methane conversion and MWCNT production. (C) 2022 The Author(s). Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.