Patients with severe asthma represent a minority of the total asthma population, but carry a majority of the morbidity and healthcare costs. Achieving better asthma control in this group of patients is therefore of key importance. Systematic assessment of patients with possible severe asthma to identify treatment barriers and triggers of asthma symptoms, including co-morbidities, improves asthma control and reduces healthcare costs and is recommended by international guidelines on management of severe asthma. This review provides the clinician with an overview of the prevalence and clinical impact of the most common co-morbidities in severe asthma, including chronic rhinosinusitis, nasal polyposis, allergic rhinitis, dysfunctional breathing, vocal cord dysfunction, anxiety and depression, obesity, obstructive sleep apnoea syndrome (OSAS), gastroesophageal reflux disease (GERD), bronchiectasis, allergic bronchopulmonary aspergillosis (ABPA) and eosinophilic granulomatous with polyangiitis (EGPA). Furthermore, the review offers a summary of recommended diagnostic and management approaches for each co-morbidity. Finally, the review links co-morbid conditions to specific phenotypes of severe asthma, in order to guide the clinician on which co-morbidities to look for in specific patients.