Abstract This work presents the durability studies carried on strain-hardening cement-based composites reinforced with 4% of 40 mm alkali treated natural curaua fiber. The collected results present the influence of natural weathering periods of 6 and 12 months on the composite tensile properties. The strain-softening behavior of the composites exposed to weathering is motivated by the deterioration of fiber-matrix bond, observed by the reinforcement work indicators, pull-out tests and visual inspection of the interfacial transition zone. Matrix specimens exposed to natural weathering provided information on pH variation along the specimen's cross-section and the chemical analysis related the pH difference to the presence of amorphous carbonates, and free from calcium hydroxide as the matrix was designed. The deterioration of post-crack fiber reinforcement capacity, thus the absence of strain-hardening behavior, was caused by fiber-matrix void observed under microscope, which deteriorated the fiber-matrix connection.