Produced water has been a big issue of water and environmental pollution. In this research, results of an experimental and modeling study on the separation of oil and salts from produced water using a rectangular flat sheet polyacrylonitrile (PAN) ultrafiltration (UF) membrane (nominal pore size of 10 nm) were analyzed. The effects of transmembrane pressure (TMP) (1, 2, 3 and 5 bar) on permeation flux of UF membranes for treatment of produced water were investigated. The results show that the average removal of chemical oxygen demand (COD) and total organic carbon (TOC) during the experiments were 94 and 83%, respectively. The UF membrane showed high potential for application in industry for produced water reusing purposes. The experimental results showed that oil retentions of almost all the membranes were over 99% and oil concentrations in the permeate were below 0.2 mg L–1. In addition, the fouling mechanism involved in UF processing of produced water was investigated by modeling. Experimental results of permeation flux were compared to the results of the fouling models. After the cake filtration model, the intermediate pore blocking model was found to predict the experimental data very well.