Sternocostoclavicular hyperostosis (SCCH), the main clinical manifestation of chronic non-bacterial osteomyelitis (CNO) in adults, is associated with various degrees of chronic pain and restricted shoulder girdle function. We evaluated the impact of CNO/SCCH on quality of life (QoL) and its determinants in 136 adult patients with this rare auto-inflammatory bone disorder using the Short Form 36, Brief Pain Inventory, Brief Illness Perception, Utrecht Coping List, and Shoulder Rating questionnaires. Data were compared with those of the general Dutch population, patients with chronic pain, fibrous dysplasia, or osteoarthritis. Eighty-six (64%) predominantly female (85%) patients with completed questionnaires were included in the study. Sixty-four (75%) had isolated CNO/SCCH. Mean delay in diagnosis was 3.0 ± 5.5 (SD) years, 90% had variable pain, and 84% limited shoulder function. Compared to healthy and chronically diseased reference populations, CNO/SCCH patients demonstrated significant impairments in almost all aspects of QoL, maladaptive illness perceptions, and ineffective coping strategies. For patients with >5-year delay in diagnosis, higher pain scores and limited shoulder function were identified as determinants for impaired QoL. Patients with CNO/SCCH reported significant impairments in QoL associated with clinical and psychological determinants. Clinical measures such as shortening delay in diagnosis, effective pain management, and psychosocial interventions targeting these factors should help minimize the negative impact of CNO/SCCH on QoL.