Aim: To evaluate the chemotherapeutic potential of a novel multifunctional nanocomposite encapsulating both porous silicon (PSi) and gold (Au) nanoparticles in a polymeric nanocomplex. Materials & methods: The nanocomposite was physicochemically characterized and evaluated in vitro for biocompatibility, cellular internalization, endosomolytic properties, cytoplasmatic drug delivery and chemotherapeutic efficacy. Results: The nanocomposites were successfully produced and exhibited adequate physicochemical properties and superior in vitro cyto- and hemocompatibilities. The encapsulation of PSi nanoparticles in the nanocomplexes significantly enhanced their cellular internalization and enabled their endosomal escape, resulting in the efficient cytoplasmic delivery of these nanosystems. Sorafenib-loaded nanocomposites showed a potent in vitro antiproliferative effect on MDA-MB-231 breast cancer cells. Conclusion: The multifunctional nanocomposite herein presented exhibits great potential as a chemotherapeutic nanoplatform.