What Is the Cause of Sinus Pain Behind the Ear?

Sinus pain behind the ear is caused by sinus stuffiness and congestion that produces pressure in the ears, explains WebMD. Congested nasal membranes can block the eustachian tube that leads to the ear and produces fluid behind the eardrum or blockage in the ear that causes pain, according to the American Academy of Otolaryngology–Head and Neck Surgery.