The concept of Γ-semihyperrings is a generalization of a semiring, a generalization of a Γ-semiring, and a generalization of a semihyperering. In this paper, we define the notions of complex product, extension property and flat Γ-semihyperrings and some of their properties are obtained. In addition, we prove that every flat Γ-semihyperring is absolutely extendable. Finally, we give some characterization of stable elements.