Objective: Adherence to low-dose aspirin is key in preventing pre-eclampsia. Midwives are well positioned to support women to take aspirin as prescribed. This study aimed to understand the barriers and facilitators that midwives face during consultations with pregnant women about prophylactic aspirin. Design, setting, and participants: A cross-sectional, UK-wide, quantitative and qualitative study of midwives was conducted between November 2020 and April 2021 using social media platforms. The survey was designed using the Theoretical Domains Framework by a team of researchers experienced in using it. An open-ended question was embedded in the survey to allow midwives to expand on matters related to the study subject. Findings: Out of 160 responders, 37.5 % indicated inadequate engagement in conversations with women about aspirin prophylaxis. Domains ‘Knowledge’ (OR 13.7, 95 %CI 5.7–32.7, p < 0.001), ‘Professional role and Identity’ (OR 15.3, 95 %CI 6.4–36.7, p < 0.001) and ‘Beliefs about capabilities’ (OR 13.6, 95 %CI 6.1–30.6, p < 0.001) were most prominently associated with effective engagement. Best fit model was comprised of ‘Beliefs about Capabilities’, ‘Social/professional role and identity’, and ‘Knowledge’. Midwives’ comments focused on barriers within ‘environmental context’ related to ‘conflicting views’ and ‘deficit in resources’ that compromise positive reinforcement of aspirin use. Responders also provided helpful ‘Top tips’ that streamline their daily practice. Conclusion and implications for practice: Beliefs about Capabilities, Social/professional role and identity, Knowledge, and Environmental Context and resources are key domains related to midwives’ engagement in conversations about aspirin in pregnancy. Clear, up-to date information for midwives and the public should be available in an easy access format to allow provision of unequivocal advice related to the use of aspirin in pregnancy.