Interlaboratory comparison can be effective to obtain consistent findings on ultrafine bubbles (UFBs). In this study, the stability of UFBs during international transportation was reported for the first time. We conducted stability tests in cooperation with German and Canadian institutions. UFBs were measured using two laser-based characterization techniques: particle tracking analysis (PTA) and dynamic light scattering (DLS). Acceleration and temperature during transportation were also measured. The results showed that regardless of transportation, the number concentration of UFBs decreased, while the size of UFBs increased with time. By filling the glass vial with UFB dispersion and minimizing the liquid flow in the vial, the effects of transportation were virtually eliminated. It was also suggested that the liquid flow caused by vibration during transportation may have enhanced the aggregation of UFBs. We report the results of an inter-instrumental comparison among PTA and DLS instruments using the transported UFB dispersions.