Purpose: Water sorption and dimensional stability of three fiber-reinforced composites were studied. Two composites (Vectris, FibreKor) were resin impregnated industrially, and one composite (Stick) was polymer preimpregnated but required further manual impregnation. Materials and Methods: Bar-shaped specimens of each material were prepared according to manufacturers' instructions. The water sorption and dimensional change of each specimen were calculated according to the change in its weight and dimension before and after immersion. Specimens were immersed in distilled water for 1, 7, 60, and 180 days. SEMs were taken to examine the quality of the fiber-matrix interface. The volume percentage of fiber content of each fiber-reinforced composite was experimentally estimated. Results: A general trend of increasing water sorption for each immersion period according to the material type was: Vectris FibreKor Stick. There were no significant differences in dimensional change among the materials and immersion periods. Conclusion: The preimpregnated fiber-reinforced composite (Stick) showed higher water sorption than the industrially impregnated fiber-reinforced composites (Vectris, FibreKor). Despite a variation in the water sorption of the fiber reinforced composites studied, all were within a 32 µg/mm3 criterion established by the ISO. The magnitude of dimensional change was small enough that it should not raise any significant clinical concern.