Titanium dioxide (TiO₂) nanostructures are one of the most plentiful compounds that have emerged in various fields of technology such as medicine, energy and biosensing. Various TiO₂ nanostructures (nanotubes [NTs] and nanowires) have been employed in photoelectrochemical (PEC) biosensing applications, greatly enhancing the detection of targets. TiO₂ nanostructures, used as reinforced material or coatings for the bare surface of titanium implants, are excellent additive materials to compensate titanium implants deficiencies—like poor surface interaction with surrounding tissues—by providing nanoporous surfaces and hierarchical structures. These nanostructures can also be loaded by diversified drugs—like osteoporosis drugs, anticancer and antibiotics—and used as local drug delivery systems. Furthermore, TiO₂ nanostructures and their derivatives are new emerging antimicrobial agents to overcome human pathogenic microorganisms. However, like all other nanomaterials, toxicity and biocompatibility of TiO₂ nanostructures must be considered. This review highlights recent advances, along with the properties and numerous applications of TiO₂-based nanostructure compounds in nano biosensing, medical implants, drug delivery and antibacterial fields. Moreover, in the present study, some recent advances accomplished on the pharmaceutical applications of TiO₂ nanostructures, as well as its toxicity and biocompatibility, are presented.