The surface tension and spectral change of the aromatic chromophore as functions of the concentration have been determined for homogeneously ethoxylated nonylphenols (NPE8, NPE10–15). Areas per molecule, surface tensions at the critical micelle concentration, and critical micelle concentrations are presented as functions of the ethylene oxide chain length. The areas per molecule increased with the degree of ethoxylation. The CMC values of homogeneously ethoxylated nonylphenols were lower than those of the octylphenol-based counterparts, higher than those of the ethoxylated nonylphenols with a natural distribution of the polyoxyethylene chains, and closely related to those of the homogeneously ethoxylated dodecylpolyoxyethylenemonoglycolethers.