Objectives Atrial fibrillation (AF) is a predominant risk factor of ischaemic stroke and treatment with oral anticoagulants (OACs) is recommended in all patients with risk factors. This study sought to examine treatment patterns of OACs in older patients with AF. Design Retrospective, cross-sectional study. Setting Danish nationwide administrative and clinical registers and databases. Participants A total of 40 027 patients, >75 years of age, after their first hospital contact due to AF between 2010 and 2018. Primary and secondary outcomes measures The primary event of interest was claimed prescriptions for OACs within 180 days after first hospital contact due to AF. Proportions of patients treated with OACs were estimated and clinical factors associated with the probability of receiving OAC treatment were identified using adjusted logistic regression models. Results A total of 40 027 patients were included with a slight majority of women (54%). The median age was 81 years (IQR 78-86). We found that an overall 32 235 patients (81%) were prescribed an OAC after their first hospital contact due to AF with a marked increase in the proportion of patients treated from 2010 to 2018. Factors related to a decreased probability of receiving treatment were bleeding risk factors such as a history of haemorrhagic stroke (OR 0.21, 95% CI 0.16 to 0.27), any bleeding (OR 0.58, 95% CI 0.53 to 0.62) as well as markers of frailty such as osteoporosis (OR 0.78, 95% CI 0.71 to 0.85). Conclusion In this large nationwide study, we found that in older patients with AF, the overall rates of OAC prescription were generally high (∼80%) and increasing during the last decade. Factors associated with not receiving guideline recommended OAC treatment were generally related to bleeding risk factors or frailty.