Herein, ultra-stable Y zeolite (USY) catalysts modified with iron doping (1, 3, and 5 wt%) using FeCl3 center dot 6H(2)O as a precursor have been investigated. Detailed characterization of the synthesized catalysts was implemented through different analytical techniques including XRD, FTIR, UV-vis DRS, NH3-TPD, H-2-TPR, N-2 physisorption, EDX, FESEM, ICP-EOS, and XRF. The strong Lewis acidity of the precursor bestowed improved acidic properties to the parent USY besides a satisfactory partial dealumination of the zeolite structure. The optimal dispersion and structural properties were obtained in the case of 1 wt% doping of iron, which eventually led to superb olefin productivity (more than 56 wt%) in the upgrading of refinery fuel oil at mild operating conditions (atmospheric pressure and 550 degrees C). The optimum catalyst (1Fe/USY) has undergone further experiments with varying temperatures and space velocities to assess the apparent kinetics based on the Arrhenius model. A threefold increase in the space velocity (from 18.3 to 54.9 h(-1)) only slightly reduced the olefin productivity of the catalyst (to 47.1 wt%), which was still notable from a heavy feedstock. Reduction of the reaction temperature to 450 degrees C led to a decrease in the olefins yield to less than a half (23.3 wt%). Overall, the modified catalysts were capable of producing a high amount of light olefins from heavy fuel oil, with an orientation toward propylene as the most favored building block in the petrochemical industries.