A simple method is presented here of organically modified molybdenum disulfide (MoS2) hindering the restack process of MoS2 nanosheets and enhancing interface interactions with a polymer matrix. The obtained f-MoS2 was introduced into a thermoplastic polyurethane (TPU) matrix to enhence its properties. Incorporated f-MoS2 nanosheets resulted in a dramatic suppression of fire hazards of TPU in terms of reduced peak heat-release rate (decreased by 45.4%), low gas degradation yield, and formation of a compact and robust char layer. After adding 2.0 wt % f-MoS2, the tensile strength of TPU increased by 40.9%. These significant reinforcements can be attributed to the tripartite cooperative mechanism of the strong interface interaction between f- MoS2 and the TPU matrix, the barrier effect of layered materials, and the catalyst action of MoS2. The facile approach can provide a novel strategy to modify MoS2 nanosheets and extend its practical application in the field of polymer composites.