<p>Much of the demand for purebred dogs in the USA is met by commercial breeding kennels (CBKs). In CBKs, adult dogs have been reported to exhibit signs of fear towards strangers. Social fear is a particular welfare concern as it may lead to acute and chronic stress in the kennel, and later, after dogs are retired and rehomed. Studies on pet and shelter dogs have shown that the type of attachment style dogs have with their caretakers is associated with their social behavior towards strangers. Thus, the aims of this study were to characterize the attachment styles of dogs from CBKs to their caretakers, and investigate relationships between the types of attachment styles observed and social fear behaviors in this population of dogs. Forty-eight adult dogs were tested from three CBKs in Indiana, USA. Each dog was subjected to a standard battery of tests, including a Secure Base test to classify attachment styles, a Stranger Arena test to measure the duration and frequency of key social behaviors toward a stranger, and a Paired-Effect test to measure the duration and frequency of social behaviors towards a stranger in the presence of a caretaker. Twenty (41.67%) dogs were classified as secure, 16 (33.33%) as insecure ambivalent, 9 (18.75%) as insecure avoidant, and 3 (6.25%) as insecure disorganized. ANOVA tests showed that secure and ambivalent dogs approached the stranger more frequently (F2,45 = 11.865, <em>p </em>< 0.001), spent more time in close proximity (F2,45 = 15.968, <em>p </em>< 0.001), and solicited contact more frequently (F2,45 = 4.58, <em>p </em>= 0.023) from them than did avoidant dogs. Wilcoxon Signed-Rank Tests showed that secure, ambivalent, and avoidant dogs all initially approached the stranger more quickly in the paired-effect test than in the stranger arena test (<em>p </em>< 0.05). Secure and ambivalent dogs also spent more time in proximity to (<em>p </em>< 0.001) and solicited more contact from (<em>p </em>< 0.01) the stranger in the paired-effect test than in the stranger arena test. These results suggest that there is an association between type of attachment style and fear behaviors towards a stranger in this sample of dogs. Understanding connections between attachment style and social fear, and their implications for stress and welfare in dogs from CBKs may help inform breeders’ selection criteria and breeding decisions. It may also inform breeders’ socialization, social interactions, and related management practices, which in turn may help to reduce dogs’ social fear and enhance their long- term welfare outcomes in the kennel. This understanding may also aid rehoming efforts. With this increased understanding, breeders could inform new owners about behaviors they can expect from their dogs which may help avoid a potential mismatch in expectations. This in turn may help keep dogs in their homes and improve their welfare in the long-term. </p>