In this study, the effect of different fiber contents (0.05%, 0.10%, 0.15%, and 0.20%) on the mechanical properties of low plasticity clay soils reinforced with raw and coated was investigated. For this purpose, reinforced specimens were axially loaded under different confining pressures (50, 100, and 200 kPa) in the unconsolidated-undrained triaxial compression test. The test results show that the stress–strain behaviour of the unreinforced soil changes from strain-softening to strain-hardening by adding hemp fiber into the soil. In general, bulging failure occurred in all specimens. The highest deviator stress at failure, energy absorption capacity and internal friction angle values were obtained in the specimen using 0.10% by-weight hemp fiber. The fibers are coated with three different water-repellent materials to protect the raw hemp fibers against biodegradation. The water absorption capacity of raw hemp fiber, measured as 218%, decreased by 127%, 213% and 159%, respectively, after coating Acrylonitrile Butadiene Styrene, epoxy, and Crystal PIB 907. Fiber’s diameters, friction surface areas, and surface roughness increased by coating raw hemp fibers. Consequently, it is found that specimens containing 0.10% by weight-coated hemp fiber had higher deviator stress, internal friction angle, and energy absorption capacity values than those containing raw hemp fiber.