Leaf stomata are the main channels for water loss of plants including cut flowers. In this study, we investigated the organographic distribution, morphological characteristics, light–dark response, and water loss contribution of stomata in cut carnations (Dianthus caryophyllus L. ‘Master’), which are prone to typical water deficits despite a few and small leaves. Stomata were observed in the upper and lower leaf epidermis, stem surface, abaxial bract epidermis, and abaxial sepal epidermis. Stomatal density (SD) on the stem surface was the highest and significantly greater than that on the upper and lower leaf and abaxial bract epidermis. The sepal epidermis had the lowest SD and the smallest stomata whereas the upper leaf epidermis had the largest stomata. Changes in the water loss rate increased in the light and decreased in the dark in both intact and leaves-removed cut carnations. The water loss rate of the former was greater than that of the latter. However, the water loss rate for the stem-only cut carnations had weak change rhythms and was much lower than that for the intact and leaves-removed cut carnations. These findings demonstrate the differential contributions of stomata in leaves, stems, and floral organs to water loss, and help to elucidate further the mechanism underlying postharvest water deficit in cut carnations.