Carbon-phenolic ablators are very efficient heat shields for atmospheric reentry vehicles: they are able to protect a capsule from hyper thermal environments characterized by intense heat fluxes (>1 MW/m 2 ) and very high temperature (also exceeding 300 C). Ablative materials can be modified by the addition of nano-fillers in order to improve their performance: small amounts of nano-fillers (in the order of 2-5 wt%) are able to enhance the matrix material properties, guarantying a weight saving too. In this work, three different kinds of ceramic nano-particles (ZrO 2 , SiC, and MgO) were tested as fillers for a phenolic resin and for a carbon-phenolic ablator: the variation in the mechanical properties and ablative performances were verified through mechanical tests and oxyacetylene flame exposure. The influence of the nanoparticles in the composite materials properties and the phenomena connected to their presence in the ablative material were deeply investigated with scanning electron microscope, EDS, XRD, and FTIR analysis.