The domestic rabbit is a popular companion animal in the UK with an estimated population of 0.9 million. Research has highlighted a large number of welfare issues related to the way rabbits are commonly kept, affecting a majority of the population. One major welfare issue is the large proportion of pet rabbits that are fearful when handled. Pet Remedy ™ (Unex Designs) is an herbal product containing valerian, marketed as a natural calming aid for reducing stress in all companion animal species. Its efficacy for domestic rabbits is previously untested. We describe a randomized, double-blind, placebo-controlled trial into the effectiveness of Pet Remedy when sprayed on an object in the environment and the clothing of a novel person handling the rabbit. A rehoming population of 50 rabbits each underwent a baseline test followed by both a placebo and a Pet Remedy treatment on three consecutive days (following cross-over design). On each day, a novel arena test was conducted, and the rabbits' behavioral responses to the experimenter measured when in its home enclosure and when being handled. Heart and respiratory rates were measured during handling. Repeated measures ANOVAs tested within-subjects differences between Pet Remedy and placebo trials, while taking into account rabbits' individual baselines. Treatment with Pet Remedy was associated with a significant decrease in heart rate during handling (F(1,42)=4.41, P=0.042) and a significant increase in the number of positive behaviors observed in a novel arena test (F(1,47)= 4.52, P=0.039). Rabbits took marginally longer to be picked up at the start of a Pet Remedy trial (F(1,47)= 4.08, P=0.049). Other variables which may have been predicted to change were unaffected. Overall the amount of rearing in the novel arena increased with day (F(1,45)=6.91,P=0.012), showing an increase in exploratory behavior with habituation. Significant individual variation occurred throughout, with almost all variables being markedly affected by an 2 individual's baseline data, and heart rates were universally high suggesting that handling is generally aversive to many rabbits. The results of this study suggest that Pet Remedy may have some potential value for rabbits during periods of acute stress, slowing heart rate and allowing the performance of more positive, relaxed behaviors. It may thus be useful during veterinary visits and during initial handling. However, given the high levels of physiological and behavioral stress exhibited, effects were small and hence we suggest optimal handling and appropriate habituation, desensitisation and counter-conditioning protocols should also be simultaneously implemented. The efficacy of pet remedy for long-term use remains untested.