BACKGROUND: National guidelines in the UK, United States of America, Canada, and Australia have recently stressed the importance of identifying and treating antenatal anxiety and depression. However, there is little research into the most effective and acceptable ways of helping women manage their symptoms of anxiety and stress during pregnancy. Research indicates the necessity to consider the unique needs and concerns of perinatal populations to ensure treatment engagement, highlighting the need to develop specialised treatments which could be integrated within routine antenatal healthcare services. This trial aims to develop a brief intervention for antenatal anxiety, with a focus on embedding the delivery of the treatment within routine antenatal care. METHODS/DESIGN: This study is a two-phase feasibility trial. In phase 1 we will develop and pilot a brief intervention for antenatal anxiety, blended with group support, to be led by midwives. This intervention will draw on cognitive behavioural principles and wider learning from existing interventions that have been used to reduce anxiety in expectant mothers. The intervention will then be tested in a pilot randomised controlled trial in phase 2. The following outcomes will be assessed: (1) number of participants meeting eligibility criteria, (2) number of participants consenting to the study, (3) number of participants randomised, (4) number of sessions completed by those in the intervention arm, and (5) number of participants completing the post-intervention outcome measures. Secondary outcomes comprise: detailed feedback on acceptability, which will guide further development of the intervention; and outcome data on symptoms of maternal and paternal anxiety and depression, maternal quality of life, quality of couple relationship, mother-child bonding, infant temperament and infant sleep. DISCUSSION: The study will provide important data to inform the design of a future full-scale randomised controlled trial of a brief intervention for anxiety during pregnancy. This will include information on its acceptability and feasibility regarding implementation within current antenatal services, which will inform whether ultimately this provision could be rolled out widely in healthcare settings. TRIAL REGISTRATION: Current Controlled Trials ISRCTN95282830 . Registered on 29 October 2014.