The nanocomposites of multiwalled carbon nanotubes (MWNTs)/titania (TiO2) were prepared by direct growth of TiO2 nanocrystals onto carboxyl-modified MWNTs under hydrothermal condition. The structure and morphology of TiO2 nanocrystals growing on MWNTs were tuned by adjusting acidity, reaction temperature, and reactant ratio. The results showed that a uniform layer of anatase TiO2 nanocrystals on MWNTs could be achieved at proper synthesis parameters. Flowerlike assemblage of rutile TiO2 nanocrystals was dispersed on MWNTs. The formation mechanism of MWNTs/TiO2 nanocomposites was further provided.