Kiwi has high antioxidant properties due to high amounts of ascorbic acid (vitamin C) and polyphenolic and flavonoid compounds and is widely consumed in the world. Kiwi juice is very popular due to its easy consumption and longer shelf life than its fruit. Processes such as concentration and clarification require the use of high temperatures or pressures, which cause the reduction of heat-sensitive compounds and the formation of undesirable compounds in the color, taste, and aroma of fruit juices. Nanofiltration is a suitable alternative for thermal processes in fruit juices due to its cost-effectiveness, high efficiency, no need for high temperature and pressure, and simplicity in carrying out the process. In this research, kiwifruit juice (variety of Hayward) was first subjected to a microfiltration process with a polyvinylidene difluoride (PVDF) membrane with a pore size of 0.22 µm and the permeate was entered into the nanofiltration process with a polyamide membrane with a cut-off of 400 Da and the process continued until the concentration of nutritional compounds. After the membrane process, in addition to determining the dominant fouling index by the Hermia model, the physicochemical properties of kiwi fruit juice such as acidity, total soluble solids, turbidity, pH, total polyphenolic and flavonoid compounds, and antioxidant properties were measured. Microfiltration and then performing the nanofiltration process resulted in the concentration of nutritional compounds that by reaching the volume concentration factor equal to 4, polyphenolic compounds increased 7 times (from about 0.0028 mg/100 cc sample to about 0.02 mg/100 cc sample) and flavonoid compounds increased about 10 times (from about 0.164 mg/100 cc sample to about 1.64 mg per 100 cc sample) were concentrated. Also, the fouling study showed that microfiltration as a pre-treatment caused the reduction of suspended particles in kiwifruit juice and delayed the fouling of the nanofiltration.