Abstract : Natural fibers such as sisal fibers have shown great promise as an alternative renewable material that can be used as reinforcement in cement-based composites. One of the ways by which sisal fibers mechanical properties can be improved to enable the fibers to compete with fiber types such as steel and synthetic fibers is through fiber surface modification. In order to improve the surface properties of sisal fibers, three fiber treatment methods namely chemical treatment, thermal treatment and hybrid treatment were carried out on the sisal fibers and the effect of these treatment methods on the mechanical properties and water absorption of the sisal fibers were investigated. Tensile tests were performed on the treated sisal fibers and their tensile strength and tensile modulus were evaluated. The experimental results showed that all the treatment methods considered led to an improvement in the tensile strength, tensile modulus and water absorption of the sisal fibers. The chemical treatment, thermal treatment and hybrid treatment led to 32.9%, 17.5% and 37.4% improvement in the tensile strength respectively. Similarly, the tensile modulus was improved by 30.9%, 13.4%, and 122% for the chemical treatment, thermal treatment and hybrid treatment methods respectively. The water absorption of the treated sisal fibers was reduced by 38.3%, 34.9% and 45.8% for the chemical treatment, thermal treatment and hybrid treatment methods respectively. The results showed that fiber treatment (chemical, thermal and hybrid) methods are effective ways of improving the mechanical properties and water absorption of sisal fibers.