The presented study examined the effectiveness of internal hydrophobization and its impact on the basic properties of cement-based materials such as paste, mortar, and concrete. The obtained results clearly indicate that, in addition to a significant reduction of the capillary water absorption, internal hydrophobization also improves the durability of the material and provides protection against water also in case of cyclic freezing and thawing. Internal hydrophobization using an organosilicon admixture based on triethoxyoctylsilane also ensured an increase in the contact angle for water to over 90 and limited moisture sorption in the material. Moreover, the presented results indicate the interactions of the organosilicon compound with cement, which can be observed as changes in the amount of heat released during cement hydration, impact on the microstructure of the mortar, and a decrease in the compressive strength of the mortar and concrete. Nevertheless, internal hydrophobization by organosilicon compounds such as triethoxyoctylsilane is an effective and efficient method of protecting porous cementitious materials against water and moisture, even during cyclical exposure to negative temperatures