The study aimed to present the differences in the mechanical characteristics of gravelly sand after adding a small amount of cement and/or fibre reinforcement. The tests were conducted on compacted non-cohesive soil – the gravelly sand or gravelly sand improved with 1.5% cement addition. Polypropylene fibres of 18 mm length were used, which were added in amounts of 0.1%, 0.2% and 0.3% to the dry mass of the soil. Gravelly sand was compacted at the optimum water content to the maximum dry density using the standard Proctor energy. The soil samples were sheared under triaxial compression conditions. Adding fibres changed the behaviour of the sample towards plasticisation of the material. The fibre content increases the maximum shear strength, which is obtained under a greater relative deformation. The failure mode of the lightly cement-bonded soil is characterized as a semi-brittle material, whereas that of the uncemented gravelly sand is the ductile mode. The failure plane of the soil with added fibres is close to horizontal, which means that the fibre-reinforced material has entered the plastic zone.