Lipophilic uranyl salophenes derivatives were used as ionophores in durable phosphate-selective electrodes. The influence of the ionophore structure and membrane composition (polarity of plasticizer, the amount of incorporated ionic sites) on the electrode selectivity and long-term stability were studied. The highest selectivity for H2PO4− over other anions tested was obtained for lipophilic uranyl salophene III (with t-butyl substituents) in poly(vinylchloride)/o-nitrophenyl octyl ether (PVC/o-NPOE) membrane containing 20 mol% of tetradecylammonium bromide (TDAB). Moreover, phosphate-selective electrodes based on this derivative exhibited the best long-term stability (2 months). The electrode durability can be improved decreasing the amount of the ammonium salt in membrane to 5 mol%.