Although it is widely accepted that dogs and humans form attachment relationships, characterizing attachment styles in dogs has only recently received attention in the literature. Previous research has shown that pet dogs display patterns of behavior in an attachment test that can be classified into secure and insecure attachment styles, much like human children and their caretakers. However, we currently know relatively little about the role of attachment styles in relation to canine well-being. This question may be of particular interest for the 3.9 million dogs that enter animal shelters in the United States alone each year, as this transition marks the dissolution of prior bonds and the establishment of new attachment relationships. Herein, results are presented from analyses of volunteer-reported canine personality and behavior measures, as well as performance on two cognitive tasks as they relate to attachment styles developed within shelter and foster environments. Results from the Canine Behavioral Assessment and Research Questionnaire (C-BARQ) indicated that foster dogs were scored as having significantly higher levels of attachment and attention-seeking behaviors when compared with shelter dogs. In both environments, dogs categorized as securely attached to a shelter or foster volunteer had lower neuroticism scores. Secure attachment in foster homes was also associated with improved persistence and performance on a point following task. These results provide support for the idea that attachment styles formed with temporary caregivers is associated with other behavioral and personality measures, and therefore may have implications for behavior and welfare in dogs living in foster homes and animal shelters.