The effect of ethane on solubilities of hydrogen and methane in toluene was identified by measuring the solubility of a ternary gas containing hydrogen, methane, and ethane and comparing with the solubility of a binary gas containing hydrogen and methane only. The ternary gas solubilities were measured at pressures up to 13.88 MPa and at a temperature of 295 K. A significant increase in the methane solubility was observed in the presence of ethane, whereas the hydrogen solubilities were little affected. The solubilities of the binary gas at pressures up to 17.33 MPa and the ternary gas at pressures up to 12.16 MPa were measured in a toluene solution containing 20 mass % eicosane. The addition of eicosane to toluene increased the gas solubilities over those of toluene alone.