Issues Addressed: A large proportion of preschoolers do not meet the recommended three hours of daily physical activity. A potential source of daily physical activity could be that provided via the family dog. This qualitative study aimed to explore the barriers and motivators to preschoolers playing with their dog and participating in family dog walks. Methods: Twelve in-depth interviews were conducted with parents of preschoolers who owned a dog. A semistructured interview guide was used, and transcripts were analysed thematically. Results: Factors influencing preschoolers playing with their dog and participating in family dog walks included parents' level of attachment to their dog, parental history of dog ownership, parent modelling of safe dog play, type of play the family dog enjoys and proximity to dog- and child-friendly destinations. Other factors such as the size, level of socialisation and perceived exercise requirements of the dog, physical environment factors such as backyard size and individual factors such as time and existing commitments were also reported. Conclusions: A number of dog, individual and physical environment specific factors should be considered when promoting preschooler physical activity through dog walking and play. So what?: A large proportion of preschoolers do not meet the recommended three hours of daily physical activity. In Australia, 43% of Australian households with children aged four to five own a dog. Dog-facilitated physical activity through family dog walks and active play could be an effective strategy for increasing preschooler physical activity.