The influence of protonated species or nonionic forms of N, N-bis(2-hydroxyethyl) dodecylamine oxide (C 12 DHEAO) on interfacial properties is studied by measuring foamability, foam stability, equilibrium surface tension and surface viscosity. Surface tensions of the protonated species with various counterions, Cl − , NO 3 − , ClO 4 − and BF 4 − show a decrease in the following order: C 12 DHEAO Cl − > C 12 DHEAO NO 3 − > C 12 DHEAO ClO 4 − > C 12 DHEAO BF 4 − . Foamability done using shaking method shows a reverse order for Cl − , NO 3 − , ClO 4 − . But the foamability of C 12 DHEAO BF 4 − is lower than that of C 12 DHEAO ClO 4 − . This has been explained in terms of the differences in the lipophilicity the micellar stability. This is further confirmed by our dynamic surface tension results. The equilibrium surface tension values for 20mM C 12 DHEAO solution shows a vague minimum in the range 4.20 < pH < 5.81. The foamability of C 12 DHEAO solution shows decrease with the values of pH. This can be elucidated by the differences in the interactions between cationic and nonionic species, nonionic and nonionic forms. The foam of protonated C 12 DHEAO having counterions Cl − , NO 3 − and ClO 4 − are very unstable. The foam stability of C 12 DHEAO BF 4 − is much greater than other protonated C 12 DHEAO. The foam stability of C 12 DHEAO solution at different values of pH shows similar order as surface tension. Foam are more stable in the range 4.20 < pH < 5.81 than that at other values of pH.