The use of training aids within equine training programmes is well established with professional, amateur and recreational riders, and horse owners. However, the claims of training aid manufacturers that the aids promote equine muscle development, gait characteristics, proprioception and the horse's biomechanics have not been evaluated scientifically. Evidence of the impact of training aids on equine behaviour and welfare is also limited. As a result, there is a limited amount of resources available to horse owners, trainers and veterinary professionals wishing to take an evidence-informed approach to the use of training aids. This review considers factors that operators should evaluate when using training aids and explores the evidence base available to help support an ethical approach to equine training and rehabilitation.