Titanium dioxide nanoparticles (TiO2NPs) have been used in a wide variety of applications, including antimicrobial activity, antifungal activity and photocatalytic activity. TiO2NPs exist in three crystalline structures: anatase, rutile and brookite. The synthesis of metal and metal oxide nanoparticles by green routes has attracted the attention of researchers because of its advantages in the protection of the global environment and public health through the decreased use of toxic chemicals. Green tea (Camellia sinensis) extracts were used for the green synthesis of TiO2NPs. TiO2NPs were characterized by UV‒visible spectrophotometry, SEM, HR-XRD, FE-TEM, EDS and FT-IR. The anatase and rutile mixture was obtained at 700 °C, whereas only rutile was synthesized at 1000 °C. Mostly irregular spherical shapes with aggregation were observed in SEM images. The extract affected the anatase/rutile content, Ti/O content and size when compared with the control TiO2NPs. At 700 °C, green tea extract resulted in the highest anatase content (94%) and the lowest Ti content. At 1000 °C, the largest rutile (87.00±9.53 nm) were synthesized. Green tea extract resulted in rutile with a relatively high Ti content at 1000 °C. To date, the effects of individual phytochemicals in the extracts on the synthesis of TiO2NPs have not been investigated in depth. We suggest that flavonoids and phenolic compounds in the extract possibly contribute to the synthesis of TiO2NPs.