Natural composites are claimed to offer environmental advantages such as reduced dependence on non-renewable energy/material sources, lower pollutant emissions, lower greenhouse gas emissions, enhanced energy recovery, and end of life biodegradability of components. In this article, natural composites based on gypsum materials reinforced with date palm fibers (DPF) are elaborated and investigated experimentally. This study is interested on the influence of the moisture on mechanical and thermal properties of lightweight gypsum composite. The experimental results showed that the adding of DPF in gypsum increases the insulation performance of the composite and decreases the mechanical strength. It’s noticed that the shrinkage of the gypsum matrix is caused by the mineralogical changes due to the dehydration of gypsum.