Solubilization of a calix[4]arene carboxylic acid derivative in an aliphatic organic solvent was accomplished by utilizing a reverse micellar solution. The reverse micellar solution was prepared by cationic cetyltrimethyl ammonium bromide (CTAB) or anionic bis-2-ethylhexyl sulfosuceinate (AOT). Both reverse micellar solutions facilitate the solubilization of the calix[4]arene carboxylic acid derivative in isooctane. The concentration of calix[4]arene solubilized in the reverse micelles increases with an increase of surfactant concentration. The water content in the reverse micelles (W-0 = [H2O]/[surfactant]) also affects the solubilization behavior of calix[4]arene. The optimum water content existed for the formation of the reverse micelles and the value was around 20. The extraction performance of calix[4]arene solubilized was investigated for yttriurn (III) in isooctane. The extraction ability of calix[4]arene was enhanced by solubilizing in the anionic reverse micellar solution.