Functionalized polymers were synthesized and applied in removing nitrogen and sulfur compounds from gas oils. In this work, the polyglycidyl methacrylate-co-ethylene glycol dimethacrylate polymer incorporated with tetranitrofluorenone, PGMA-DAP-TENF, was synthesized with and without alumina support. Different techniques were used to characterize the synthesized polymers including Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller method, dynamic light scattering, thermogravimetry/differenial thermal analyzer, carbon hydrogen nitrogen sulfur elemental analysis, and field emission scanning electron microscopy. The performance of the polymer with alumina, Al-PGMA-DAP-TENF, was compared to that without alumina using light gas oil. In addition, heavy gas oil feed was used to confirm the adsorption behavior of both polymers in a higher nitrogen and sulfur environment. The effect of adsorption time and temperature was tested using a 1:5, by weight, polymer to feed ratio. Results have shown that alumina particles enhanced the nitrogen removal efficiency of PGMA-DAP-TENF polymer while sulfur removal efficiency was not affected. The nitrogen removal efficiency of Al-PGMA-DAP-TENF polymer was more than twice that of PGMA-DAP-TENF polymer in LGO feed, and twice that in HGO feed. This was due to the higher surface area of Al-PGMA-DAP-TENF polymer, 202 m2/g, compared to that of PGMA-DAP-TENF polymer, 27 m2/g. In addition, Al-PGMA-DAP-TENF polymer removed more basic nitrogen compounds than PGMA-DAP-TENF polymer. This was attributed to the acidic nature of alumina particles that enhance the adsorption of basic nitrogen compounds present in gas oil feeds.