Background and aims: Object attachment is the emotional bond or connection that we have with possessions. Although thought to be ubiquitous, when excessive, object attachment is presumed to contribute to compulsive buying and hoarding problems. Unfortunately, our understanding of this relationship has been limited by the constraints of existing object attachment measures. In this paper, we developed and validated a new self-report questionnaire, called the Object Attachment Security Measure (OASM). Methods: We developed an item pool based on previous measures and consultation with 24 experts in the field. After piloting, we administered this measure to a large sample (Final N 5 365), along with self-report measures of hoarding, compulsive buying, and previous object attachment measures. Results: We found that the OASM distinguished between secure and insecure object attachment. Both subscales showed excellent internal consistency and test-retest reliability over a two-week period. Additionally, they demonstrated excellent convergent and divergent validity, and criterion validity with measures of hoarding and compulsive buying symptoms. We also found that insecure, but not secure object attachment, was uniquely related to hoarding and compulsive buying symptomology. Discussion and conclusion: Our findings extend theoretical models, highlighting the role of insecure object attachment. Future research in both clinical and consumer behaviour fields should utilise the OASM, as reducing insecure object attachment and potentially encouraging secure object attachment could decrease maladaptive possession use and increase sustainable consumption.  Kulcsszavak: object attachment, hoarding disorder, compulsive buying-shopping disorder, measure development, attachment style, consumer behaviour