The finite element analysis is used to investigate the sensitivity of the effective transverse thermal conductivity of polymeric composites reinforced with Manila hemp fibers in terms of their degree of saturation. It is predicted that the hierarchical structure of the fiber bundle will highly magnify the rate of water absorption and in consequence, the effective transverse thermal conductivity of the composite is altered. This influence is quantized in terms of the volume fraction of the fiber bundle and the lumen to produce a homogenized representative continuum. It was found that increasing the fiber volume fraction in a dry medium results in a decrease in the thermal conductivity whereas an increase of conductivity will be evident in a wet condition. Furthermore, the increase in the volume fraction of the lumen enhances the thermal conductivity by retaining more water during saturation which supports the developed hypothesis.