Recently, the polymeric materials have extensive uses because of their amazing combination of properties, durability, light weight and simplicity of processing. However, these materials face some problems like their weak thermal stability and also poor mechanical stability. Therefore, a large number of additives especially metal nanoparticles were added to polymeric matrix to overcome these problems and designed polymer matrix nanocomposite. A composite is defined as the combination between two individuals or more than one material by physical or mechanical method to get a new material with unique and elegant structure and properties and carrying the feature of the two separated materials and distinguishable interface. Many approaches are used to prepare the polymer nanocomposites such as ex situ, in situ and radiolytic methods. The nanocomposites have important features such as excellent mechanical properties like high stiffness, strength, toughness; good chemical properties like corrosion resistance; and high physical properties like high optical, mechanical, thermal, low density and specific antibacterial properties. The nanocomposite materials with these higher properties have a wonderful and different range of functional applications. The deep view on the synthesis strategies and physical properties of the polymer/noble metal nanocomposites is offered in this book and also their applications in many fields.