We report a one-step facile synthesis of a novel MgO nanoparticle/metal organic framework (MOF) composite. Mg-MOF-74 was thermally decomposed under a hydrogen atmosphere to produce MgO nanoparticle/MOF. This product was characterized by X-ray powder diffraction, infrared spectroscopy, and transmission electron microscopy. The mean diameter of MgO nanoparticles in the composite was 2.5 +/- 0.7 nm.