Introduction: Deferral of consent for participation in a clinical study is a relatively novel procedure, in which informed consent is obtained after randomisation and study treatment. Deferred consent can be used in emergency situations, where small therapeutic time windows limit possibilities for patients to provide informed consent. We aimed to investigate patients' or their proxies' experiences and opinions regarding deferred consent in acute stroke randomised trials., Patients and Methods: For this qualitative study, Dutch Collaboration for New Treatments of Acute Stroke (CONTRAST) trial participants were selected. Study participants were either patients or their proxies who provided consent and were selected with theoretical sampling based on patient characteristics. Semi-structured interviews were conducted face-to-face or by telephone. Themes and subthemes were iteratively defined., Results: Twenty of the 23 interviewed participants (16 patients and 7 proxies) considered deferred consent acceptable. The received study treatment and consent conversation were remembered by 18 participations, although the concept of randomisation and treatment comparison were generally not well understood. Sixteen participants felt capable of overseeing the decision to give deferred consent. Distress in the first days after stroke, lack of understanding and neurological deficits were reasons for feeling incapable of providing consent. Four participants would have preferred a different timing of the consent conversation, of whom two prior to treatment., Conclusion: Our study found that deferred consent was considered acceptable by most study participants who provided consent for acute stroke randomised trials. Though they felt capable, the recall and comprehension of consent were overall limited., Competing Interests: Declaration of conflicting interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: SAvdB: grants (Remmert Adriaan Laan Fund). YBWEMR: shareholder (Nicolab). DD: grants (Dutch Heart Foundation, Brain Foundation Netherlands, Netherlands Organisation for Health Research and Development, Health Holland Top Sector Life Sciences & Health, Penumbra Inc., Stryker, Medtronic, Thrombolytic Science LLC, Cerenovus for research)., (© European Stroke Organisation 2021.)