An experimental investigation has been conducted to characterize the performance of a two-phase ejector with different mixing tube length ratios. In a two-phase ejector with an optimum mixing tube length, complete mixing between a primary jet and suction flow can occur within the mixing tube. Because geometrical and operating parameters have interconnected effects on ejector performance, the ejector design should be optimized by simultaneously considering these parameters, to achieve higher performance in two-phase ejector application systems. Measurements have been performed in ejectors with five mixing tube length ratios, all with a diffuser area ratio of 3.0. Primary and suction-flow rates at their respective inlets, together with the static pressures at the inlets, have been measured using mass flowmeters and pressure transducers. All tests have been carried out within a Reynolds number ranges of 0.99 × 105 - 2.66 × 105. The results indicate significant improvements in entrainment and pressure-lifting with an increase in the mixing tube to critical length ratio of 16.67. The enhancement in entrainment is due to the increase in traction force, resulting from the enhancement of the mixing between the primary jet and suction flow, whereas the enhancement in pressure lifting is d...