Aim The aim of this study was to explore patients’ experiences of preventive anticoagulation therapy in atrial fibrillation. Design This was a descriptive qualitative study based on interviews. Methods Individual interviews with 15 patients, 6 women and 9 men, treated with preventive oral anticoagulant due to atrial fibrillation, were conducted. The interviews were analysed with qualitative content analysis. Results Based on the analysis, the theme Managing a necessary evil emerged. The theme comprised the three categories: Coping with anxiety and changes in daily life, Having confidence in care and Being a partner or only a receiver of treatment. Patients described it like being faced with a situation where a treatment perceived as vital was weighed against undesirable consequences and risks. Patients trusted caregivers and had confidence in care, but there was a risk of being a receiver of care instead of becoming a partner.