A great deal of attention has been given in the last years to the study of the influence of incorporating nanosized particles and particularly nanoparticles with a flat-like morphology such as nanoclays or layered double hydroxides, in the properties of polymer nanocomposites. The high aspect ratio of these nanofillers could result in improved interactions with polymer molecules at low filler concentrations, maintaining some of the main advantages of polymer composites such as reduced density. These improved interactions could lead to mechanical improvements or enable to regulate polymer nanocomposites' properties such as transport properties or even improve their intrinsically low flame retardancy. Recently, polymer foam preparation and characterization has gained a lot of attention, as foams have been shown to extend the range of properties and thus possible applications of polymers. The combination of foaming with the incorporation of nanosized particles (polymer nanocomposite foams) could further extend the material's properties, as nanoparticles could have a direct effect in the cellular structure of the foamed material and thus in its final properties. This chapter pretends to give a review of the most recent studies carried out on the influence of layered nanoparticles, focusing on silicate nanoclays and layered double hydroxides, on the mechanical and flame retardancy properties of polymer foams, with the final goal of developing multifunctional lightweight materials with improved properties for applications in sectors such as construction or automotive.