For last decade, alkanethiolate self-assembled monolayers (SAMs) on gold have been intensively studied due to their potential applications in many areas including surface coating, sensor development, etc. Although most SAMs have been prepared in organic solvents such as ethanol, toluene, dimethylformamide (DMF), dimethylsulfoxide (DMSO), there has been growing interest in SAMs prepared from aqueous medium in the presence of various surfactants. The surfactants in the solution form micellar structure, giving rise to increased solubility of water-insoluble thiols. This method provides an environmentally friendly and biologically compatible route compared to conventional technique, but details regarding the mechanism of formation and the effects of surfactants on SAMs need further investigation. In this work, the structure of dodecanethiol (DDT) SAMs onto gold from SDS solutions were prepared by changing SDS concentration, DDT concentrations, and reaction time. The structures of these SAMs were investigated by Fourier transform infrared spectroscopy with attenuated total reflectance mode (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). The concentration of SDS was found to have a more profound effect on the structure of DDT rather than other conditions.