A prospective study on the product distribution at chemical equilibrium for the simultaneous liquid-phase etherification of isobutene and isoamylenes with ethanol over Amberlyst¿ 35 is presented. Experiments were performed isothermally in a 200 cm3 stirred tank batch reactor operating at 2.0 MPa. Initial molar ratios of alcohol/olefins and isobutene/isoamylenes ranged both from 0.5 to 2, and temperature from 323 to 353 K. Reactants equilibrium conversion, selectivities and yields toward products were clearly affected by the experimental conditions. Experimental etherification yields have been modeled using the response surface methodology (RSM), combined with the stepwise regression method to include only the statistically significant variables into the model. The multiobjective optimization (MOO) of etherification yields has been carried out numerically, by means of the desirability function approach, and graphically, by using the overlaid contour plots (OCP). Optimal conditions for the simultaneous production of ethyl tert-butyl ether (ETBE) and tert-amyl ethyl ether (TAEE) have been found to be at low temperatures (323 to 337 K) and initial molar ratio alcohol/olefins close to 0.9 and isobutene/isoamylenes close to 0.5.