Denatonium benzoate (DB) is an extremely bitter tasting chemical to humans and is used as a deterrent in various products where ingestion is unwanted, including antifreeze, laundry detergent, and treatments to discourage nail biting. In the case of antifreeze, some formulations contain ethelyne glycol, which is toxic not only to humans but also to dogs, cats and other mammals. DB serves as a deterrent for all vulnerable species, but published data on its efficacy in dogs and cats is not available. In this study we assessed the sensitivity of dogs to DB in vivo and then investigated the responses of dog bitter receptors (Tas2r) to DB in vitro. We found that in a two-bottle choice test 10 miniature schnauzer dogs on average did not reject a solution of 10μM (4.47ppm) DB (p = 0.883) but a larger sample (31 miniature schnauzers, 26 Labrador retrievers, 19 cocker spaniels) on average did reject 100μM (44.66ppm) (p <0.001), although this was not true for every dog on every exposure. Accordingly, dog Tas2rs were less sensitive to DB than their human orthologues, with dTas2r4 being the only sensitive receptor (EC₅₀ = 3.78mM). In humans TAS2R47 Is the most sensitive receptor for DB, followed by TAS2R10. Dogs lack a functional orthologue for TAS2R47 but do have one for TAS2R10. However, we found that dTas2r10 was completely insensitive to DB. By generating and testing a series of dog/human chimeric Tas2r10 receptors we identified that this difference was related, at least partly, to differences in the second extracellular loop (ECL2) region. We hope these data will help to inform the debate on the use, inclusion rate, and selection of bitter deterrents when considering dogs and also stimulate further research on the efficacy of bitter taste deterrents in other vulnerable species.