Er:In:LiNbO3 crystals were grown by Czochralski method from congruent melts containing 0.5/0.5, 0.5/1.0, and 0.5/1.5 mol%/mol% Er2O3/In2O3. The Er and In concentrations in the crystals were determined by neutron activation analysis. The refractive indices at the 473, 633, and 1536 nm wavelengths were measured by prism coupling technique. The unpolarized Er3+ and OH absorption spectra of the crystals were measured at room temperature. The Er3+ absorption cross-section spectra were determined, and the Er3+ spectroscopic properties were analyzed by Judd–Ofelt (J–O) theory. The In segregation coefficient is 1.20 ± 0.06, 0.95 ± 0.05, and 0.89 ± 0.05, respectively, and the Er concentrations in all of the three crystals studied have a nearly same value of 1 mol%. The ordinary index decreases while the extraordinary index increases with the increased In doping level. The 0.5 and 1.0 mol% In2O3-doped two crystals are below while the 1.5 mol% In2O3-doped crystal is above the photorefractive threshold concentration. The Er3+ absorption cross sections of some transitions change definitely due to In codoping, but reveal a weak dependence on the In2O3 doping level. The J–O-predicted spectroscopic parameters show similar In codoping effects. The In codoping hardly affects the Er3+ 1.5 μm radiative lifetime.