The combination of chitosan and metal oxides was utilized as an addition to improve the fouling resistance of polyethersulfone (PES) ultrafiltration membranes. Pure water flux, membrane hydrophilicity by the contact angle, scanning electron micrographs, and Fourier-transform infrared spectra were used to characterize the membranes. With the addition of metal oxides, the modified membrane’s water flux increased. The PES membrane with 0.25% wt chitosan and 2.0% wt AgNO3 had the highest flux and antibacterial activity among the membranes tested. Because of its potential to improve membrane hydrophilicity, the water flux increased with the addition of chitosan and AgNO3. Because of the improved hydrophilicity, the contact angle reduced as chitosan and Ag loading was increased. The PES–chitosan–Ag2O (from AgNO3 2.0% wt) membrane had high antibacterial activity against Escherichia coli and Staphylococcus aureus, whereas the PES–2.0% wt Ag membrane did not show the same result. Finally, the addition of chitosan in the PES–Ag membrane increased the membrane’s antibacterial activity substantially.