A new poly(ether-amide; PEA) as a source of polymeric matrix, containing flexible ether group in the main chain was synthesized by direct polycondensation reaction of 1,2-(4-carboxy phenoxy)ethane with 4,4-diaminodiphenyl ether in a medium consisting of N-methyl-2-pyrrolidone, triphenyl phosphite, calcium chloride, and pyridine. The resulting PEA was characterized by gel permeation chromatography (GPC), H-1 NMR and FT-IR spectroscopy. Magnesium Hydroxide (MH) nanostructure was synthesized by the reaction of magnesium sulfate and sodium hydroxide by sonochemical method. The MH particle was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Then Mg(OH)(2) nanostructure was added to poly(ether-amide) matrix and resulting nanocomposites were characterized by XRD, SEM, and Thermogravimetry Analysis (TGA). Thermal decomposition of the PEA shifted towards higher temperature in the presence of the magnesium hydroxide nanoparticles. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 2004-2009, 2013