The present study investigates the impact of post annealing of TiO2 nanoparticulate films on their crystallinity, mechanical strength, and morphology. Non-agglomerated and amorphous TiO2 nanoparticles of 46 nm diameter were synthesized in a plasma field, and were subsequently deposited on substrates to form nanoparticulate films. The films were annealed at various temperatures in the range of 100-1,200 degrees C. Phase transformations from amorphous-to-anatase and from anatase-to-rutile were observed at 400 degrees C and at 1,000 degrees C, respectively. The high rutile transformation temperature was considered to be due to a tensile field induced by shrinkage of the film. The as-deposited film and the films annealed at below 400 degrees C had poor mechanical strength. Conversely, the films annealed at over 500 degrees C were strengthened by necking of the nanoparticles. The size of nanoparticles changed with increasing temperature. Annealing at 100-300 degrees C caused the nanoparticles to shrink to approximately 30 nm. The nanoparticle diameters changed only slightly when annealed at 400-600 degrees C because the annealing time was insu efficient for changes to manifest. Annealing at 700-900 degrees C caused the nanoparticle diameter to increase to approximately 50 nm because of sintering and coalescence of the nanoparticles. The diameter of the nanoparticles annealed at over 1,000 degrees C became approximately 200 nm because of densification during the anatase-to-rutile transformation. The porosities of the films annealed at below 900 degrees C were over 80%. However, the porosities of the films annealed at over 1,000 degrees C decreased significantly due to densification.