This study deals with the effect of water absorption on the physical and mechanical properties of the glass fiber/waste cotton fabric hybrid composites compared to the samples with maleic anhydride (MA) as coupling agent. Water absorption studies were performed for four different soaking times of 100, 250, 500, and 1000 h at room temperature. To clearly understand how long this type of composites can endure without any important loss of mechanical properties, tensile and impact tests were performed after 500 and 1000 h of water immersion time. Results showed that using MA can reduce water sorption values significantly from 5% to 1.5%. In addition, very limited variations in tensile properties were explored even after 1000 h of soaking time by the presence of MA. On the other hand, impact test results revealed that changes in impact strength values are very complex and different mechanisms play a role with respect to the hybrid formulations. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45506.