One of the most interesting processes in energy-related catalysis is steam-assisted catalytic cracking. Herein, ZSM-12 (MTW) zeolite was modified by impregnation to improve the selectivity to olefins in the presence of steam. ZSM-12 zeolite was synthesized hydrothermally and modified by incorporating ZSM-12 zeolite with lanthanum (La), cerium (Ce), and boron (B). Two different ammonium solutions were used in the ion-exchange of the synthesized ZSM-12 zeolite, namely, ammonium nitrate and ammonium fluoride. Each group was impregnated with 2 wt % of lanthanum, cerium, or boron. Catalytic performance was evaluated using steam catalytic cracking of n-hexane. H-ZSM-12 zeolite exchanged with ammonium nitrate and impregnated with lanthanum and cerium has conversion above SO C-mol %. However, impregnation with boron reduced the active sites, and the conversion was 20 C-mol %. On the other hand, exchanging the samples with ammonium fluoride led to the loss of the active sites and the conversion was around 20 C-mol % in the presence of lanthanum, cerium, and boron.