A new modification process for the preparation of organoclay has been devised. Functional organoclay nanofillers (FONs) based on the mixing of bentonite and other inorganic fillers such as fumed silica, aluminium trihydroxide (ATH) and sepiolite were prepared and employed to obtain composites of ethylene-vinyl acetate and ATH. These composites were characterised by means of X-ray diffraction, thermogravimetric analysis, mechanical and fire retardant properties. The results confirmed that the modification process for the preparation of FONs is able to influence the intercalated structure of the clay, and hence the mechanical properties and behaviour as flame retardant materials.