Acute calcific tendinitis of the longus colli muscle in the cervical spine is an uncommon benign condition caused by calcium hydroxyapatite deposition in its tendon and a subsequent inflammation. Clinical diagnosis is difficult because its incidence is rare and it can be misdiagnosed as retropharyngeal abscess, traumatic cervical spine injury, or infectious spondylitis. Therefore, a definitive diagnosis requires evaluation of the plain radiogram and a combination of CT and MR imaging. In this report we describe a case with calcific tendinitis of the longus colli muscle with satisfactory results after conservative treatment.