The influence of the addition of ethylenediamine and L-Lysine.HCL on the micellization process of sodium lauroyl sarcosine (SLAS) in aqueous solution was studied using an electrical conductivity technique. The conductivity data were used to determine the critical micelle concentration (CMC) and degree of counter-ion dissociation () in the temperature range 288.15–318.15 K. Thermodynamic properties of micellization (ΔG°mic, ΔH°mic, and ΔS°mic) were evaluated using a mass action model. The results showed that the CMC values of SLAS decreased with increases in the ethylenediamine and L-Lysine.HCL concentrations in aqueous solution. The extent of this effect followed the order: ethylenediamine < L-Lysine.HCL. Furthermore, the CMC of SLAS enhanced with increases in temperature for all systems studied. The  values of SLAS increased in the presence of the ethylenediamine and L-Lysine.HCL. The calculated thermodynamic parameters indicated that the micellization of SLAS is spontaneous and entropy driven in the absence and in the presence of ethylenediamine and L-Lysine.HCL within the temperature range investigated.