The surface modification of iron oxide magnetic nanoparticles (MNPs) with gum Arabic (GA) via adsorption and covalent coupling was studied. The adsorption of GA was assessed during MNP chemical synthesis by the co-precipitation method (MNP_GA), and after MNP synthesis on both bare magnetite and MNP_GA. The covalent immobilization of GA at the surface of aldehyde-activated (MNP_GA(APTES)) or aminated MNPs (MNP_GA(EDC)) was achieved through free terminal amino and carboxylate groups from GA. The presence of GA at the surface of the MNPs was confirmed by FTIR and by the quantification of GA by the bicinchoninic acid test. Results indicated that the maximum of GA coating was obtained for the covalent coupling of GA through its free carboxylate groups (MNP_GA(EDC)), yielding a maximum of 1.8g of GA bound/g of dried particles. The hydrodynamic diameter of MNPs modified with GA after synthesis resulted in the lowest values, in opposition to the MNPs co-precipitated with GA which presented the tendency to form larger aggregates of up to 1mum. The zeta potentials indicate the existence of negatively charged surfaces before and after GA coating. The potential of the GA coated MNPs for further biomolecule attachment was assessed through anchorage of a model antibody to aldehyde-functionalized MNP_GA and its subsequent detection with an FITC labeled anti-antibody.