The development of novel prostate-specific membrane antigen (PSMA)-targeted radioactive theranostic agents is currently limited to facilities capable of working with high-energy radioisotopes. Even preselection of lead structures in vitro relies mostly on radioactive assays with PSMA(+) LNCaP and PSMA(-) PC-3 cells. Assays utilizing radioisotopes are time consuming, costly, and limit discovery to a small group of scientists with special facilities. Nonradioactive alternatives are therefore needed in the field. In this paper, we describe an inductively coupled plasma mass spectrometry (ICP-MS)-based method for the evaluation of PSMA-targeting ligands conjugated to DOTA-chelates of Europium. This method is based on LNCaP and PC-3 cells and has been validated with the well-established targeting ligand PSMA-617.