A polyolefin graft polyamide composition incorporating lamellar nanofillers. Also, a tube, pipe or analogous formed from a multilayer at least one of the layers of which contains this composition. A thermoplastic composition having a polyolefin backbone containing a residue of at least one unsaturated monomer and a plurality of polyamide grafts, and also another component, wherein: the polyamide grafts are attached to the polyolefin backbone by the residue of the unsaturated monomer comprising a function capable of reacting via a condensation reaction with a polyamide having at least one amine end group and/or at least one carboxylic acid end group, the residue of the unsaturated monomer is attached to the backbone by grafting or copolymerization, wherein the other component consists of platy nanofillers, said nanofillers being phyllosilicates and representing from 1% to 6.5% by weight of the composition.