Retanning process aims at filling up of the meatuses of the already tanned leather through the incorporation of vegetable or synthetic tannins or polymer (resins) with the aim of giving more fullness and improving to the final product. In this research, poly(methyl methacrylate-co-butyl acrylate) emulsion was prepared in situ with nano-silica in order to be used as a modern retanning agent of chrome tanned leather to totally replace chrome salt and to enhance physical, thermal shrinkage, and mechanical properties of the final tanned leather as well as to reduce the environmental impact of chrome tanning effluent. Polymer/nano-silica hybrid emulsions were prepared via in situ seed emulsion polymerisation. The prepared polymers were characterised for solid content, molecular weight, viscosity, drying time, minimum film-forming temperature (MFFT) and microstructures (via TEM). The mechanical, shrinkage, thermal and surface morphological (by SEM) properties of the treated samples were also investigated. The influence of the increase in the content of organic nano-silica on the properties of the retanned leather were also discussed.