Tetrafunctionalized resorcinarene cavitands (4−6) have been synthesized starting from tetrakis(bromomethyl)cavitand 3. New cavitand-based cation ligands with (carbamoylmethyl)phosphonate (CMP) and -phosphine oxide (CMPO) moieties (8a,b and 9a,b) were prepared via two different routes in good (45−86%) overall yields. The ligands (8a,b and 9b) are very effective europium extractants. Ph2CMPON(Pr)-cavitand 8b has the highest extraction constant, determined with radiotracer experiments, for 1:1 complexation with Eu(picrate)3 (Kex1 = 2.7 × 1012 M-4). The steric preorganization of the four CMP(O) moieties on the resorcinarene cavitand improves the efficiency and selectivity [of Eu(III) over UO2(II) and Fe(III)] of the metal extraction processes, compared to simple CMP(O) extractants.