The aim of our study was to investigate whether citronella-spray collars offer a humane alternative to electric-shock collars to reduce the barking of domestic dogs. The Aboistop collar was applied to seven dogs with problematic barking behaviour by the dogs’ owners in a series of case studies concurrently run. Vocalisation of the dogs was recorded in the problem context under baseline conditions, inactive collar conditions, and active collar conditions. The Aboistop collar was effective at reducing problem vocalization for only three of seven dogs and appeared to be most effective for dogs whose problem barking had developed more recently. The collar may be more humane than other punishment methods, but it did produce stress reactions which varied in severity across the dogs. Clinical Relevance. In our study, the collar was applied by the dogs’ owners in order to test whether the collar would be effective when used by members of the public. While the results here are preliminary, they suggest that the collar may be effective for some dogs, but not for others, when applied by dog owners for the treatment of problem vocalisation. Further research is required to determine whether the collar could be effective when administered by a trained professional.