In this work, we reported the synthesis, characterization of Ce-doped titania nanotubes (Ce-TNTs), and application in flame retardancy of an intumescent flame-retardant polystyrene (PS/IFR) system. The flame retardancy of polystyrene (PS) composite that was composed of pentaerythritol, microencapsulated ammonium polyphosphate, and PS was enhanced significantly by adding a small amount (0.1 wt%) of (Ce-TNTs). The thermal properties of the flame-retardant PS were investigated by thermogravimetric analysis, limiting oxygen index (LOI), vertical burning test (UL-94), scanning electronic microscopy, dynamic mechanical thermal analysis, and the real-time Fourier transform infrared spectrometry (FTIR). The maximal decomposition rate temperature of PS/IFR containing Ce-TNTs in air is much higher than that of other PS composite without Ce-TNTs. The LOI value of PS/IFR that contained 0.1 wt% of Ce-TNTs was increased from 27.0 to 28.5, and the UL-94 rating was also enhanced to V-0 from no rating when the total loading of additive was the same. The real-time FTIR showed that the degradation process was changed after the addition of TNTs. All results indicated that Ce-TNTs had a significant synergistic effect on the flame retardancy of PS/IFR. Copyright © 2012 John Wiley & Sons, Ltd.