The aim of this research was to prepare rare metal (Er, Yb)-modified TiO₂ nanoparticles by a sol-gel method. The obtained nanoparticles were characterized by BET measurements, UV-Vis spectra and the Laser-induced fluorescence (LIF) method. Visible light photocatalytic activity of the sample was studied by photodegradation of phenol while considering the influence of the dopant concentration. The obtained results showed that a smaller amount of the dopant gave better photocatalytic activity of a semiconductor. The absorption spectra of Yb³⁺-doped and Er³⁺-TiO₂ samples show stronger absorption in the UV– Vis region than pure TiO₂. The presence of erbium was found more beneficial for visible light activation of TiO₂ doped photocatalysts than ytterbium.