Glue ear occurs due to inadequate ventilation of the middle ear, usually due to dysfunction of Eustachian tube, the tube that joins the back of the nose to the middle ear. It is very common in young children due to the configuration of the Eustachian tube. Children with glue ear may also have enlarged adenoids.

An important cause of glue ear in adults in Singapore is nasopharyngeal cancer (NPC, or cancer at the back of the nose). Nasopharyngeal cancer is the most common head and neck cancer in Singapore and occurs mainly in people of southern Chinese origin.