In this present work, the composites were obtained from carbon quantum dots and TiOf via green synthesis and the photoactivities of these composite structures were investigated under ultraviolet light. Carbon quantum dot was obtained from Stachys euadenia which is an endemic plant found only in southern Türkiye. Carbon quantum dot-TiO2 nanocomposites were fabricated via facile hydrothermal approach which is an easy and effectual method to obtaining of environmentally friendly, low cost and well crystallized nanoparticles. The structural and morphological characteristics of these nanocomposites were investigated by X-ray diffraction, tunneling electron microscopy and scanning electron microscopy. Also, optical analyses of carbon quantum dots were carried out by absorbance and fluorescence spectroscopy. Photocatalytic activity of TiO2 and carbon quantum dot-TiO2 nanocomposites were investigated under ultraviolet light illumination with the decomposition of methylene blue dye. Carbon quantum dot-TiO2 nanocomposites show a better activity than TiO2.