Expansive soils are one of the problematic soils that are spread in many countries including Iran. The swelling potential of the untreated expansive clay sample was extremely high, thus the soil sample provided for the study was considered in the very high expansion category. Nanosilica and polypropylene fibers were used as the stabilizing and reinforcing materials. The results indicated that the swelling potential of one-day cured samples by the addition of nanosilica decreased moderately, and the improvement by means of nanosilica and polypropylene fiber decreased the swelling potential significantly. It was observed that the increase of curing time led to a decrease in swelling potential and an increase in UCS. To investigate the durability of the soil samples, the effects of freeze-thaw cycles on the volume changes and strength reduction rate of treated and untreated samples were measured. The highest strength reduction rate occurred after the 1st and 2nd cycle such that it was much lower for the treated samples by the optimal content of additives compared with the untreated one. In addition, the maximum volumetric strain for the untreated expansive clay was measured two times higher than that of the sample treated by nanosilica and polypropylene fiber simultaneously. The results of microstructural tests confirmed the strong potential use of a combination of nanosilica and polypropylene fiber in reducing the negative effects of freeze-thaw cycles on the soil characteristics.