A new synthetic route for polyethylene (PE)/exfoliated MoS2 (EMoS2) nanocomposites using novel Ziegler–Natta catalyst intercalated MoS2 was designed. The catalyst was synthesized by the intercalation of MoS2 with a Grignard reagent, followed by anchoring of TiCl4 into the MoS2 galleries. The intercalated MoS2 was exfoliated to form PE/EMoS2 nanocomposites during in situ ethylene polymerization. The resultant PE/EMoS2 nanocomposites had a layered morphology, and they were well dispersed in the PE matrix. In addition, the thermal stability and mechanical properties of PE were significantly enhanced with the introduction of EMoS2. Thus, this work provides a facile approach to the production of PE/EMoS2 nanocomposites.