Oil palm fibers represent a very abundant and natural resource for raw materials that can be efficiently utilized as reinforcement in polymers. The sorption characteristics of two types of oil palm fibers-oil palm empty-fruit-bunch (OPEFB) fiber and oil palm mesocarp fiber-in distilled water, mineral water, and water containing salt at four different temperatures were investigated. The uptake of water decreased with an increase in temperature. The OPEFB fiber showed higher sorption than the mesocarp fiber. This was due to the uptake associated with the capillary action in the OPEFB fiber. The thermodynamic parameters of the sorption process were calculated.