A major obstacle to the development of a more efficient calcium phosphate bone cement (CPC) is its relatively low mechanical strength and susceptibility to brittle fracture. Herein, a series of dual-setting hybrids have been developed based on the in situ crosslinking polymerization of glycidyl methacrylate derivatized dextran (Dex-MA) and the synchronous hydration process of CPC. Such a strategy is highly desirable for bone regeneration and provides insight into hybrid cement designing. The structure and physical properties of the resulting hybrids are investigated. Compared with CPC, the initial setting time is shortened and may be modulated. As a result, the hybrid cement possesses characteristics of both of its components, and is tunable from stiff-but-not-brittle to ductile-but-not-soft depending on the composition of the double network. Introduction of the polymeric moiety does not obstruct the fundamental hydrating process of CPC. Due to the synergistic effect produced by the double-network structure, the resulting hybrid has an optimal compressive strength of over 98.3 MPa. The mass ratio of the binary network and the size of apertures are shown to be key parameters for improving the compressive strength.