The effects of paclobutrazol (PBZ) on the ex vitro transfer efficiency of in vitro grown Dendrobium nobile seedlings were investigated. The survival percentage was increased by 41.6 % with 0.8 mg dm−3 PBZ treatment compared to controls. The PBZ-treated D. nobile plants were shorter than control plants. Morphological and anatomical analyses showed that root diameter, especially at the root apex, became larger after treatment with PBZ which is consistent with the increases in cortical cell sizes and row numbers. In addition, the first observations of thickened velamen of the PBZ-treated seedling were made in the present study. The activities of cellulase and indole acetic acid oxidase increased in PBZ-treated plantlets, whereas that of cell wall-associated peroxidase declined compared to controls. The content of endogenous gibberellic acid and iso-pentenyladenosine of root tips changed little by PBZ but that of indole-3-acetic acid decreased by 53 %. These results indicated that PBZ could improve the transfer efficiency of D. nobile from in vitro culture to pots due to its effects on root development.