This article deals with the water absorption behavior of low-cost polymer composite composed of carpet waste jute yarns and thermoset matrices (i.e., epoxy and polyester). The water absorption behavior of the composites and deviation of their flexural and impact properties after aging in distilled water were investigated. The magnitude of diffusion parameters such as n and K were evaluated to assess the mode of water transport. It was found that the composites follow Fickian diffusion behavior. Both maximum water content (M(max)) and effective diffusion coefficient (D(eff)) values increased with increasing fiber content. Epoxy matrix composites showed higher M(max) and D(eff) values when compared to those of polyester matrix composites. D(eff) value increased remarkably with an increase in immersion temperature, whereas temperature had relatively little impact on M(max) value. Thermodynamics of diffusion process was investigated using Arrhenius plots and the magnitude of the activation energy for the process of diffusion (E(a)) was evaluated. E(a) increased with temperature increment, suggesting fast access of water into polymer segments at elevated immersion temperatures. NaOH treatment of jute yarns was also investigated in terms of the water absorption behavior of the composites. It was shown that alkali treatment reduces water absorption of the composites remarkably, which was attributed to interface improvement. Flexural strength and modulus of the composites decreased up to 40% and 60%, respectively, whereas Charpy impact strength increased up to 30% after 168 h of water immersion.