Exacerbation is a defining feature of severe asthma, and oral corticosteroids (OCSs) are frequently prescribed to manage exacerbations. This qualitative study was conducted to examine the experience of patients with severe asthma, with a focus on asthma exacerbation and OCS treatment. Adults with severe asthma were recruited from three tertiary hospitals in South Korea. Data were collected through in-depth qualitative interviews. Verbatim transcripts were analysed using Colaizzi's phenomenological method to uncover the meaning of the participants' experience. Recruitment of participants continued until thematic saturation. 14 patients with severe asthma were recruited. Four theme clusters emerged: 1) experience of asthma exacerbation; 2) impact on life; 3) OCS treatments; and 4) disease perception. The patients experienced severe physical and psychosocial distress from asthma exacerbations, felt helpless due to failed efforts to prevent exacerbation and were living a restricted life due to fear of exacerbation. They feared OCS side-effects but had no other choice than to rely on OCSs because other interventions were ineffective. Most had poor knowledge and understanding of severe asthma and the long-term health consequences. Asthma exacerbation affects wide aspects of life in patients with severe asthma. Several components may underlie reliance on OCSs, including experience of distress during exacerbation, fear of future exacerbation and lack of proper knowledge about the long-term health consequences of severe asthma and OCS treatments. A multi-disciplinary approach is warranted to support the patients and to provide systematic education about the long-term health implications of severe asthma.