The microhardness-nanostructure correlation of a series of silica/silicon oxycarbide porous composites has been investigated, as a function of pyrolysis temperature, T-p. The pyrolyzed products have been studied by means of scanning electron microscopy, mercury porosimetry, chemical analysis, solid-state Si-29-NMR, X-ray diffraction, Raman spectroscopy, and microindentation hardness. Two distinct regimes are found for the microhardness behavior with T-p. In the low-temperature regime (1000degreesC less than or equal to T-p < 1300degreesC), the material response to indentation seems to be dominated by the large amount of pores present in the samples. In this T-p range, low microhardness values, H, are found (<110 MPa). Above T-p = 1300degreesC, a conspicuous H increase is observed. In this high-temperature regime (T-p = 1300-1500degreesC), microhardness values are shown to notably increase with increasing pyrolysis temperature. The H behavior at T-p = 1300-1500degreesC is discussed in terms of (i) the volume fraction of pores and the average pore size, (ii) the bond density of the oxycarbide network, and (iii) the occurrence of a nanocrystalline SiC phase.