Some children form an attachment to a variety of inanimate objects, such as cloths or soft toys, referred to as attachment objects. This study examined the developmental change in children's behaviours toward their attachment objects to understand the role of such objects through an online survey of 700 parents with 0- to 9-year-old children, of whom 417 currently had attachment objects. Zero- and one-year-olds selected cloths and soft toys equally and used them with their mouth or skin, whereas older children preferred soft toys and personified them. Our results suggest that the role of attachment objects changes with age and that attachment objects contribute to reducing stress responses.