Non-tuberculous mycobacterial (NTM) infections present a major challenge in both diagnosis and treatment. The management of NTM varies based on the species involved and the host's risks factors. With their prevalence continuing to rise, healthcare professionals are likely to encounter these infections more often in the years ahead. It is therefore essential to be aware of the predominant NTM species in our environment, as well as the associated risk factors. In this context, we present a study conducted at the University Hospital of Liège between 2016 and 2020, aimed at identifying the NTM species responsible for infections in the Liège area. We also explore the immune mechanisms involved in fighting these infections, focusing on primary immunodeficiencies that should be considered in adult patients with NTM infections.