Dendrobium orchid is one of the most popular cut flower and potted plants. In this study, a protocol for efficient genetic transformation of D. nobile-type orchids was established by co-cultivating 21 day-old protocorms for 3 days with Agrobacterium tumefaciens strain EHA101 carrying pIG121Hm harboring β-glucuronidase (GUS) gene as reporter gene and hygromycin phosphotransferase (hpt) gene as selectable marker gene. After selection of the infected protocorms on New Dogashima (ND) medium containing 10 g l⁻¹ maltose, 30 mg l⁻¹ hygromycin and 20 mg l⁻¹ meropenem for 3 months followed by the culture on hygromycin-free recovery medium for 1 month, secondary protocorm-like bodies (PLBs) produced on this medium were again transferred onto secondary selection (regeneration) medium. Plantlets were successfully regenerated from these secondary PLBs after the transfer. The highest transformation efficiency of 27.3% was obtained when protocomrs were inoculated with 10 times diluted Agrobacterium solution (OD₆₀₀=0.1) for 300 min. Transformation of the selected plants was confirmed by GUS assay, PCR and Southern blot analysis. This protocol could be adopted to produce transgenic D. nobile-type orchids with various traits such as novel flower color and resistances to biotic and abiotic stresses.