Introduction and importance: Horner syndrome, an oculo-sympathetic pathway disorder, is a very rare manifestation of cervical spine pathologies which usually present with either axial neck pain, radiculopathy, or myelopathy symptoms (or combinations of these). It is more-likely to happen in the upper cervical level involvement. Case presentation: A 44-year-old male presented with a complaint of right eyelid drop two months before admission. The symptom was accompanied by radicular neck pain and weakness of the right upper extremity (M4) since 1 month earlier. An MRI revealed a cervical herniated disc at the C5–6 spine level. Clinical discussion: The patient underwent open discectomy followed by cervical disc replacement. Symptoms were significantly improved following surgery. Conclusion: In the presence of cervical symptoms, a focused evaluation of Horner syndrome can be done, and symptom resolution can be expected after the appropriate treatment. Otherwise, a thorough examination must be obtained to find the pathology along the tract of the oculo-sympathetic pathway and prevent irreversible neurological disturbance. © 2023 The Author(s)