The influences of temperature, manganese, and carbon on the surface tension of liquid ternary Fe-Mn-C systems were investigated. The measurements were carried out with the sessile drop method in the temperature range of 1653-1834 K. The manganese and carbon contents were changed between 4.79-9.89 and 1.07-4.20 wt%, respectively. It was demonstrated that the surface tension varied as a linear function of temperature for all the examined samples. With increasing manganese content, the surface tension decreased. When the weight fraction of manganese with respect to iron was fixed, the surface tension decreased with increasing carbon content. From thermodynamic consideration, it was considered that carbon preferentially adsorbed on the metal surface as carbon atoms rather than manganese carbide.