Herein, MoS2 nanosheets (MoS2) densely modified with n-octadecyl mercaptan (NOM) are used as effective friction-reducing and antiwear additives. A facile and green strategy is employed to prepare the organic inorganic hybrid nanosheets (MoS2 NOM) by mussel-inspired chemistry combining with the Michael addition reaction. When MoS2 NOM nanosheets are added in poly-alpha-olefin (PAO) 10, they form a homogeneous and stable dispersion compared to the unmodified MoS2. Tribological measurements show that the dispersion of PAO 10 containing 1 wt % MoS2 NOM displays dramatic reductions in the friction coefficient (similar to 53%) and wear volume (similar to 92%). The exceptional tribological behaviors of MoS2 NOM are ascribed to the formation of a boundary protection film during tribochemical reactions. Further investigations display that the addition of 1 wt % MoS2 NOM can efficiently improve the maximum load-carrying capacity and the high-temperature lubricating property of PAO 10 base oil, which is likely due to the formation of n-octadecyl thioether on the surface of MoS2 after the modification of MoS2 polydopamine (PDA) with NOM via Michael addition.