Loading of quercetin onto drug cargo is still progressively studied to not only improve its solubility but also control the release behavior for improving therapeutics efficacy. In this present study, we successfully prepared drug cargo based magnetically porous cellulose (PC) functionalized by amine‐based alkoxysilane (MPC−NH2) for effectively carrying and sustainably delivering quercetin. The PC derived from oil palm empty fruit bunches provides high loading capacity reaching 344.48 ± 5.69 mg/g with loading effectiveness of 67.02 ± 1.11%. Surface modification of PC surfaces by Fe3O4 nanoparticles and aminosilane compounds not only enhances the quercetin loading effectiveness to 80.83 ± 1.10% but also controls the quercetin release behavior either at artificial gastric or physiological condition. The kinetic release study elaborates that anomalous transport is mainly involved during release of quercetin under physiological condition, but the Fickian diffusion plays the role at artificial gastric condition. The kinetic release rate of quercetin calculated following Higuchi model indicates that the Que@MPC−NH2 has slower release rate compared to another drug carrier. Additionally, the antioxidant activity of quercetin is significantly improved after being loaded onto MPC−NH2. Finally, we recapitulate that the loading of quercetin within MPC−NH2 is a powerful strategy for improving loading capacity, drug‐release ability, and antioxidant activity.