BackgroundExtended brief interventions (EBIs) are effective in targeting alcohol misuse in the general population. However, little is known of the effects of EBI in adults with intellectual (also known as learning) disabilities. In this feasibility trial we compared EBI with usual care for alcohol misuse in adults with mild to moderate Intellectual Disability (ID).MethodsThe study took place in three community ID networks of services in England. Participants aged 18–65 years with reported alcohol problems, a score ≥8 on the Alcohol Use Disorder Identification Test (AUDIT), and IQ <70 (+/5%CI) were recruited and were randomly allocated to either EBI (five weekly sessions and one follow-up at 8 weeks) and usual care or usual care alone. Research assistants were blind to arm allocation. Research assessments took place at baseline, 2 and 3 months. The primary outcome was reduction in alcohol consumption measured by the AUDIT. Preliminary health economic analysis was performed to investigate the costs of delivering EBI and the feasibility of a cost-effectiveness analysis in a full trial. The trial is closed.ResultsParticipants were recruited from January 2014 to August 2015. Thirty individuals were randomised (15 in each arm) and provided primary outcome data. In regard to harmful drinking, at baseline, all the participants exceeded the relevant threshold. At 8 weeks, the proportion of participants with harmful drinking had decreased to 60% for both groups, and at 12 weeks it had decreased by 66°7% and 46°7% for the intervention and the control groups, respectively. The unit cost for the delivery of EBI is £430.ConclusionsRecruitment to this trial has been proven challenging as prevalence of alcohol misuse in the targeted population was lower than anticipated. EBI may provide an effective low-intensity treatment for this population. Participants’ and carers’ feedback on their experience was overall positive. Further work needs to be undertaken to ascertain the group of participants that should be participating in a future definitive trial.Trial registrationPsychological Intervention Alcohol Misuse Learning Disability; isrctn.com, identifier:10.1186/ISRCTN58783633. Registered on 17 December 2013.Electronic supplementary materialThe online version of this article (doi:10.1186/s13063-017-1953-0) contains supplementary material, which is available to authorized users.