This study investigates the reactive melt grafting of maleic anhydride (MAH) onto low-density polyethylene (LDPE) using dicumyl peroxide (DCP) as a radical initiator, with particular emphasis on the effect of Irganox 1010 on grafting efficiency and gel formation. The effects of MAH and DCP concentrations, together with Irganox 1010, dimethylformamide (DMF), and methanol, were systematically evaluated. Grafting increased with increasing MAH and DCP contents; however, the addition of Irganox 1010 produced a pronounced increase in MAH grafting, despite its conventional role as a phenolic antioxidant. This finding indicates that Irganox 1010 can facilitate the grafting reaction under reactive melt-processing conditions, potentially through a synergistic interaction with DCP-generated radicals. Importantly, the increased grafting in the presence of Irganox 1010 was accompanied by suppression of gel formation, demonstrating a favorable shift in the competition between MAH grafting and polyethylene crosslinking. Aromatic additives and their combinations further affected grafting efficiency, with the synergistic additive systems yielding the highest grafting levels. FTIR spectroscopy confirmed successful MAH incorporation through the characteristic carbonyl absorption bands of grafted anhydride groups. The melt flow index decreased progressively with increasing grafting degree, reflecting increased molecular weight, chain entanglement, and the contribution of crosslinked structures, particularly in samples with higher gel fractions. Overall, the results establish Irganox 1010 as an effective additive for enhancing MAH grafting onto LDPE while limiting undesirable gel formation, highlighting its potential to improve the efficiency and controllability of reactive melt functionalization processes.