Simple SummaryHuman–animal interactions consist of many relationship types. The human–dog bond is one such example. This study reviewed how we measure the human–dog bond through questionnaires and found a lack of questions related to the dog’s investment in said bond. To rectify this, twelve semi-structured interviews were carried out with a variety of dog guardians to investigate their views on how their dogs showed that they shared a bond with them. The common themes that emerged included ‘affirmation’, ‘understanding of a dog’s preferences, likes, and dislikes’, and ‘adaptation’. These themes provide a useful foundation from which to design new questions within human–dog bond questionnaires. This would allow better representation of a dog’s investment in the bond and, therefore, help create tools that reflect the reciprocal nature of this relationship.Dogs play an important role in many western societies, providing companionship, emotional support, and assistance, as well as other more specialist roles. The literature reveals that many human–animal interaction (HAI) questionnaires exist to measure the human–dog bond (HDB). The first part of this study assessed how far existing questionnaires went in measuring HDB (defined as the unique, dynamic and reciprocated relationship between a person and dog, one in which each member can influence the other’s psychological and physiological state). A systematic literature review revealed that a common limitation in HDB questionnaires was a lack of questions based on the dog’s investment in the bond and, therefore, a failure to measure the two-way characteristic of the HDB. This led to the second part of the study: to identify novel themes relating to dog investment in the HDB from which new tool questions could be developed. This was investigated qualitatively using twelve semi-structured interviews on HDB, undertaken with participants from a variety of dog–guardian relationship types. HDB themes that emerged included ‘adaptation’, ‘understanding of a dog’s preferences, likes, and dislikes’, and ‘affirmation’. Subthemes included ‘boundaries’ and ‘expectations’ (within adaptation), ‘excitement’, ‘proximity’, ‘affection’, and ‘recall’ (within affirmation). The themes that arose provide a foundation from which to build new lines of questioning within HDB tools. Such questioning can better represent a dog’s investment in the HDB and, therefore, help create tools that reflect the reciprocal nature of a bond more accurately.