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Several treatments on natural fibers are presented by literature as effective process to mitigate the high water absorption and reduce dimensional variation. The wetting and drying cycles treatment is pointed as an efficient treatment since they promote the stiffening of the polymer structure of the fiber cells, known as hornification. One of the main characteristics of this process is the greater dimensional stability of the fibers. In this context, the objective of the present research is to investigate the influence of wetting time, fiber/water ratio and number of wetting and drying cycles on the treatment and its effect on sisal fibers chemical and mechanical properties. The treatment of the fibers was performed in water at room temperature (T = 22 °C), varying wetting time (1h and 3h) and fiber/water ratio (1:10 and 1:40), drying process 80°C during 15 hours. Direct tensile tests, thermogravimetry analysis (TG) and infrared spectroscopy (FTIR) were performed on raw, pre-washed and treated fibers. The results revealed that lower fiber/water ratios are better to hornification promotion. Immersion times of 3 hours were efficient to increase stiffness in all studied cases.