Organic modification of MoSe2 sheets is firstly achieved by Atherton-Todd reaction, aiming at the acquisition of multifunctional MoSe2 hybrid. Simultaneous enhancements in fire safety and mechanical property of thermal plastic polyurethane (TPU) are obtained with the presence of this hybrid. Strong interfacial interactions between the functionalized MoSe2 sheets and TPU can be obtained, making more efficient load transfer from the weak polymer chains to the robust sheets. Besides, more coherent barrier network may be formed in polymer matrix, restraining the diffusion of decomposed fragments and reducing the supply for combustion fuel. Consequently, the decreases in heat release are observed for polymer composites. Notably, the releases of toxic gases, such as HCN and CO, are also suppressed by this barrier network, resulting in the reductions in fire toxicity. This work may open a new door for the functionalization of MoSe2 sheets and evoke significant developments in its promising applications.