The equilibrium phase densities, vapor phase compositions, and interfacial tensions of the ternary mixture (methane + ethane + n-pentane) have been measured simultaneously using the pendant drop technique at 294.15 K. The total mole compositions of the measured ternary mixtures are 50.61 % methane + 8.93 % ethane + 40.46 % n-pentane; 34.20 % methane + 6.04 % ethane + 59.76% n-pentane; and 17.46% methane + 3.08% ethane + 79.40% n-pentane, respectively. The measured phase densities and vapor phase compositions are compared with calculated equilibrium properties from the GERG2004 equation. No open interfacial tension data for these ternary systems have been reported at any isothermal conditions. The average experimental interfacial tension data can be described with the total deviations of about 3.2 %. The combined standard uncertainty at each experimental condition is calculated on the basis of ISO recommendations.