Escherichia coli is often used as a faecal indicator bacterium to evaluate water quality and is used as a measure to predict the presence of pathogens and their inactivation/removal is important to ensure safe drinking water. In this study γ–Fe2O3 nanoparticles were synthesized by a modified sol–gel method, followed by a subsequent functionalization process with Moringa oleifera (MO) integral seed extract and without ethanol‐extracted oil (MO‐et) for the creation of a new coagulants with antibacterial activity (γ–Fe2O3–MO and γ–Fe2O3–MO(et)). These coagulants were characterized according to their composition, morphology, structure, and surface charge. Coagulation/flocculation tests were performed with subsequent sedimentation under the influence of an external magnetic field for E. coli inactivation/removal. The results indicate that there was total inactivation of E. coli for raw water and removal of 88 and 93% for synthetic water using the coagulants γ–Fe2O3–MO and γ–Fe2O3–MO (et) respectively, demonstrating that the coagulant properties of MO and the superparamagnetic behavior of nanoparticles of γ‐Fe2O3 increased the activity of the new material, favoring the inactivation/removal of E. coli in the water treatment.