Purpose: To report a rescue technique for complete removal of an accidentally ruptured orbital dumbbell deep dermoid cyst. Observations: A 33-year-old female presented with left proptosis with retrobulbar discomfort for 3 months. Computed tomography images showed an orbital dumbbell deep dermoid cyst. A lateral orbitotomy was performed under general anesthesia. The cyst was ruptured during osteotomy of the lateral orbital rim. The cyst was opened vertically from the ruptured site using a Stephen's tenotomy scissors to visually confirm the internal wall of the cyst and to keep the epithelial lining intact while separating the external wall of the cyst from the bone. There was a small defect of the epithelial lining at the inferoposterior margin of the cyst. Granulomatous inflammation of the lacrimal gland was found adjacent to the defect site. The cyst was completely removed and the lacrimal inflammation subsided after the operation. Conclusions and importance: Opening of the cyst is a useful technique to remove the entire epithelial lining of an accidentally ruptured dumbbell dermoid cyst. Keywords: Dumbbell, Dermoid cyst, Rupture, Epithelial lining, Opening of cyst