The equilibrium phase densities and interfacial tensions of the binary mixture (ethane + n-pentane) have been measured simultaneously using the pendant drop method at 294.15 K. The experimental pressure was in the range of (6 to 30) bar. The measured phase densities are compared with calculated equilibrium densities by applying the GERG2004 equation. The deviations of the measured interfacial tension at each experimental condition are calculated on the basis of ISO combined standard uncertainty calculation recommendations. No open interfacial tension data for the system have been reported at any isothermal conditions. The measurement results extend the range of previous interfacial tension data of the hydrocarbon mixtures in the open literature.