Simple SummaryThe aim of this study was the scientific validation of a novel instrument (the Mourning Dog Questionnaire) designed to allow a comprehensive quantitative analysis of grief responses in dog owners after the death of a pet dog, which is a still underestimated issue. This instrument was based on a grid of quantitative measurable outcomes that combines five different questionnaires concerning levels of attachment to pets, responses to the loss of a pet, outlook on life events and grief, perceptions of animals in terms of emotions, needs and legal right. We found that pet owners have the tendency to humanise their pet and perceive animals no differently from humans in terms of emotions, needs and legal rights. In addition, after the death of the pet, a negative view of life was described according to the findings. The Mourning Dog Questionnaire could be a useful tool considering the high numbers of people who are at risk of experiencing the loss of a companion dog, which makes this type of grief as potential major concern for public health and human welfare.AbstractPeople often develop strong emotional connections with their dogs and consider them to be members of the family. The purpose of this study was to develop a novel validated tool, the Mourning Dog Questionnaire, to recognise and evaluate the mourning process in people who have lost a dog. The research model was based on a grid of five different questionnaires: the Pet Bereavement Questionnaire, the Lexington Attachment to Pets Scale, the Animal-Human Continuity Scale, the Positivity Scale, and the Testoni Death Representation Scale. The Italian version of the survey was posted on social networks. A sample of 369 Italian dog owners filled in the questionnaire (mean age ± SD 42.00 ± 10.70 years). Reliability indices were good for all instruments. The total scores of the five questionnaires correlated with each other. The results from the Mourning Dog Questionnaire support the negative view of life after the death of a pet and people’s tendency to humanise their pet, since dog owners perceived animals no differently from humans in terms of emotions, needs and legal rights. Findings arising from the use of the Mourning Dog Questionnaire will help the implementation of rationality-based strategies to improve the wellbeing, resilience and quality of life of people in the world experiencing the loss of a pet.