Titanium dioxide (TiO2) nanotube has been considered to be a suitable material for photocatalyst applications. In this study, TiO2 nanotube was synthesized using Degussa P25 nanoparticles through a hydrothermal process at 150°C for 24 hours. This was followed by a post-hydrothermal process with temperature variations of 80,100,120 and 150°C for 12 hours. The post-hydrothermal results were further characterized using x-ray diffraction (XRD), followed by a matching procedure towards ICDD-JPDS data and regression analysis using General Structure Analysis System (GSAS) software. This study aims to investigate the effect of post-hydrothermal temperature on crystallite sizes, density, unit cell volume and lattice parameters of TiO2 nanotubes using Rietveld analysis. The results showed that all synthesized samples consisted of the TiO2 anatase phase. It was observed that the crystallite size increased from 5.788 to 14.647nm at a post-hydrothermal temperature from 80 to 120°C. Meanwhile, when the temperature was increased to 150°C, the size of the crystallite decreased from 14.647 to 12.490nm. Furthermore, the Rietveld analysis results using GSAS software showed that the optimum density and minimum cell unit volume required to cause a change in the lattice parameter at the lattice constant c of 5.9950 Å and temperature of 100°C are 9.035gr/cm3 and 29.40Å3, respectively. Based on the refinement using GSAS software, it was also shown that increasing the temperature during the post-hydrothermal process results to a better phase match value, which is a wRp and Rp value of 9.73% and 6.72%, respectively. Simultaneously, the best linearity was obtained at a higher temperature of 150°C, with a goodness of fit value of 2.171. This shows that increasing post-hydrothermal temperature leads to the successful formation of well-defined anatase TiO2 crystal structure.