In this work, the first-principles calculations on the structural, electronic and optical properties of lanthanides (Ln)-doped anatase TiO2 using Ln elements from cerium (Ce), neodymium (Nd) and erbium (Er) were performed to observe the effects of Ln doping that can improve the properties of TiO2. The Ln-doped TiO2 has lower band gaps compared to pure TiO2 due to the presence of impurity energy levels (IELs) from Ln 4f states which can be seen from the density of states (DOS). Among the Ln-doped TiO2, the shift of light towards a longer wavelength spectrum is from Nd-doped TiO2. Overall, the first-principles study from the deepest atomic level in this work can clarify the Ln doping effects in TiO2.