We report a Chinese patient who presented with metastatic undifferentiated carcinoma in the cervical lymph node of unknown primary origin. Despite a raised IgA titre against Epstein‐Barr virus capsid antigen, examination and biopsy of the nasopharynx were negative. Radiotherapy was given to the head and neck region with the orbit shielded. There was complete resolution of the metastatic lymph nodes. She developed proptosis of her left eye one year afterward when a large tumour was found in the lacrimal sac region. Review of the initial computerized tomography revealed a small soft tissue mass in the same region. The tumour was composed of undifferentiated carcinoma cells associated with dense lymphoid infiltrate. In situ hybridization for Epstein‐Barr virus EBER RNA showed strong positive signals in the malignant cells. This is the first reported case of an Epstein‐Barr virus positive undifferentiated carcinoma with lymphoid stroma in the lacrimal sac. In addition to the nasopharynx, salivary glands, nasal cavity and paranasal sinuses, the lacrimal sac should be considered as a potential primary site for Epstein‐Barr virus positive metastatic undifferentiated carcinoma in the cervical lymp