Background: Osteogenesis Imperfecta (OI) is characterized by bone fragility, and features such as blue sclerae, dentinogenesis imperfecta, hearing loss, ligamentous laxity and short stature can be present. It has long been assumed that the functional ability and quality of life of patients with OI depends primarily on the severity of skeletal deformities. However, fatigue is often mentioned in clinic by patients with all types of OI as an important modifier of their quality of life and does not always seem to be related to their functional ability. The aim of this study is to investigate whether adults with Osteogenesis Imperfecta are significantly more fatigued than the normal population. Methods: The Fatigue Severity Scale (FSS) was distributed by mobile phone application among 151 adult patients with different OI types. Results of the FSS in the OI group were compared with two control populations from America (n = 20) and the Netherlands (n = 113). Results: Ninety-nine patients (OI type 1 (n = 72), OI type 3 (n = 13), OI type 4 (n = 14) completed the FSS questionnaire. The mean FSS score of this cohort was 4.4 and significantly higher than the control populations (2.3/2.9). 65% of our cohort reported at least moderate fatigue compared with 2 control populations from America and the Netherlands. Conclusion: Fatigue in patients with OI is a frequently encountered problem in our expert clinic but research into this topic is sparse. This pilot study is the largest study to date investigating fatigue in patients with OI and results have been compared with two control groups. The mean FSS score of 4.4 in the OI group indicates that people with OI are generally significantly more fatigued than the control population. Further evaluation of fatigue and its influencers in a larger group of OI patients is important for future management.