In this paper, we have developed a facile and general strategy to enhance the stability of multilayers incorporating nanoparticles and the weak polyelectrolyte poly(allylamine hydrochloride) (PAH). Using Fe₃O₄ nanoparticles (Fe₃O₄ NPs) and Au nanoparticles (Au NPs) as separate model systems, after multilayers of nanoparticles and PAH were constructed employing the layer-by-layer (LbL) technique, 4,4′-diazostilbene-2,2′-disulphonic acid disodium salt (DAS) was post-infiltrated into the multilayers and subsequent photochemical cross-linking was completed under UV irradiation. The stability of multilayers with Fe₃O₄ NPs and Au NPs were both improved significantly, and less than 15% of the nanoparticles were lost from the multilayers after an intensive agitation. The UV-visible spectroscopy and atomic force microscopy measurements supported the improvement of the stability of the multilayers.