Ab initio calculations for the Er3+ ion are performed using GRASP2K package, based on multiconfigurational Dirac-Hartree-Fock method (MCDHF). 41 energy levels of the [Xe]4f 11 con- figuration are calculated. The study includes different types of correlations using different strategies. The Breit interaction and leading QED effects are included as perturbations in all calculations. We present the results of the 10 lowest levels (see Table 1), obtained by single and double excitations corresponding to valence, core, and core-valence correlations. Levels are notated in the form (2S+1)L Nr J , where instead of the group labels νW U, single character ”numbers” Nr are used. Deviation of our values for energy levels from NIST database reaches 6.9%. Energy levels given at NIST are derived from the spectrum of Er3+ in LaF3 [1].