Intracellular retention of functional vasopressin V2 receptor (V2R) is a major cause of congenital nephrogenic diabetes insipidus (NDI) and rescue of V2R mutants by non-peptide antagonists may restore their basolateral membrane (BM) localization and function. However, the criteria for efficient functional rescue of G-protein coupled receptor (GPCR) mutants at clinically-feasible antagonist concentrations are unknown. We found that the four non-peptide antagonists SR49059, OPC31260, OPC41061 and SR121463B induced maturation and rescued the BM expression of eight out of nine different V2R mutants, stably-expressed in physiologically-relevant polarized cells. The extent of maturation and rescued BM expression correlated with the antagonists concentration and affinity for the V2R. Displacement of the antagonists by AVP and subsequent cAMP generation inversely correlated with the antagonists affinities for the V2R, but is partially influenced by antagonist-specific aspects. Despite limited increases of maturation and cell-surface expression of V2R mutants, the low-affinity SR49059 optimally induced functional rescue at high concentrations, due to its easy displacement by vasopressin. At clinically-feasible antagonist concentrations, however, only the high-affinity antagonists OPC31260 and OPC41061 induced functional rescue, as at these concentrations the extent of BM expression became limited. In conclusion, functional rescue of mutant V2Rs at clinically-feasible concentrations is most effective with high-affinity antagonists. As OPC31260 and OPC41061 are clinically safe, they are promising candidates to relieve NDI. Moreover, as numerous other diseases are caused by ER-retained GPCRs for which cell-permeable antagonists become available, our finding that high-affinity antagonists are superior is anticipated to be important for pharmacotherapy development of these diseases.