In the past decade, a variety of drug carriers based on mesoporous silica nanoparticles has been extensively reported. However, their biocompatibility still remains debatable, which motivated us to explore the porous nanostructures of other metal oxides, for example titanium dioxide (TiO 2), as potential drug delivery vehicles. Herein, we report the in vitro hemolysis, cytotoxicity, and protein binding of TiO 2 nanoparticles, synthesized by a sol–gel method. The surface of the TiO 2 nanoparticles was modified with hydroxyl, amine, or thiol containing moieties to examine the influence of surface functional groups on the toxicity and protein binding aspects of the nanoparticles. Our study revealed the superior hemocompatibility of pristine, as well as functionalized TiO 2 nanoparticles, compared to that of mesoporous silica, the present gold standard. Among the functional groups studied, aminosilane moieties on the TiO 2 surface substantially reduced the degree of hemolysis (down to 5%). Further, cytotoxicity studies by MTT assay suggested that surface functional moieties play a crucial role in determining the biocompatibility of the nanoparticles. The presence of NH 2–functional groups on the TiO 2 nanoparticle surface enhanced the cell viability by almost 28% as compared to its native counterpart (at 100 μg/ml), which was in agreement with the hemolysis assay. Finally, nonspecific protein adsorption on functionalized TiO 2 surfaces was examined using human serum albumin and it was found that negatively charged surface moieties, like–OH and–SH, could mitigate protein adsorption to a significant extent.