We present for the first time experimental measurements on the ultrafast population dynamics of the model surface-active dye methyl orange (MO) during its ion transfer across the water|1,2-dichloroethane interface by using time-resolved surface second harmonic generation (TR-SSHG). The interfacial dynamics reveals that the population of MO relaxes to the ground state within 160 fs without any significant contribution of the molecular reorientation. It is concluded that the MO transfer across the interface considerably affects the population of MO at the interface but has no effect on the dynamics of the molecule itself.