The β^--particle-emitting erbium-169 is a potential radionuclide toward therapy of metastasized cancer diseases. It can be produced in nuclear research reactors, irradiating isotopically-enriched ¹⁶⁸Er₂O₃. This path, however, is not suitable for receptor-targeted radionuclide therapy, where high specific molar activities are required. In this study, an electromagnetic isotope separation technique was applied after neutron irradiation to boost the specific activity by separating ¹⁶⁹Er from ¹⁶⁸Er targets. The separation efficiency increased up to 0.5% using resonant laser ionization. A subsequent chemical purification process was developed as well as activity standardization of the radionuclidically pure ¹⁶⁹Er. The quality of the ¹⁶⁹Er product permitted radiolabeling and pre-clinical studies. A preliminary in vitro experiment was accomplished, using a ¹⁶⁹Er-PSMA-617, to show the potential of ¹⁶⁹Er to reduce tumor cell viability.