This paper presents congenital anomalies characteristic of Klippel–Feil syndrome, type II, diagnosed in the skeleton of a young to middle‐aged woman uncovered in a cemetery adjacent to the Church of St. Jacob the Apostle in Wągrowiec (Poland), from a grave within an archaeological layer dated to the 14th–17th centuries. A rare type of fusion was identified between the sixth and seventh cervical vertebrae only, co‐occurring with a well‐developed right cervical rib fused to the shaft of the first thoracic rib and articulated via synovial joints with the seventh cervical vertebra. The fusion of the cervical vertebrae involved their bodies, right laminae, and parts of the right articular processes. The interpretation of the presence of Klippel–Feil syndrome is additionally supported by the absence of any evidence of trauma in the cervical region of the spine or of pathological changes in the skeleton indicative of diffuse idiopathic skeletal hyperostosis or ankylosing spondylitis. The formation of Schmorl's nodes and degenerative changes in apophyseal joint surfaces diagnosed in the cervical vertebrae were probably secondary in relation to the observed congenital anomalies. Additionally, examinations revealed ossified insertions of the ligamentum flavum and degenerative changes of the vertebrae in the lower region of the spine as well as incomplete posterior bridge of the atlas, torus mandibularis, and humerus septal aperture.