AbstractNanobubble (NB) water has been shown to promote the growth of several types of plants and animals, but the mechanism underlying this promoting effect remains unclear. The present study evaluated the mechanism by which NBs maintain the freshness of cut flowers by keeping cut chrysanthemum (Chrysanthemum morifolium Ramat.) flowers at the bud stage in vase water containing air NBs. The condition of petals and leaves was assessed to determine the vase life of these cut flowers. The NB treatment delayed bud opening and petal senescence of the inflorescences. Water absorption and transpiration by cut flower stems were lower in NB water than in distilled water (DW). Furthermore, when all the leaves were removed from the cut flower stems, no significant difference in vase life was observed between NB water and DW. These findings indicate that the inhibition of transpiration from leaves prolonged the vase life of NB‐treated cut chrysanthemum flowers. In the early stage of the treatment, NB treatment significantly reduced transpiration without closing stomata, suggesting that the reduction in transpiration observed in the NB‐treated plants might be due to the suppression of cuticular transpiration, defined as water loss through the epidermis. Surface tension, one of the important driving forces of water movement in plants, was not affected by the presence of NBs in water. To our knowledge, this is the first report to show that transpiration from leaves is inhibited by NB treatment.