We assessed the reliability and validity of the Defense Mechanism Rating Scale (DMRS) when used with the Adult Attachment Interview (AAI) and compared defensive functioning among women with and without binge-eating disorder (BED). Participants were women with BED (n = 101), overweight/obese women without BED (n = 47), and normal weight women without BED (n = 49). Participants completed the AAI, and self-report measures of interpersonal distress, reflective functioning, and attachment insecurity. Coders rated the DMRS and reflective functioning from AAI transcripts. We found acceptable interrater reliability on the DMRS; significant correlations between the DMRS and interpersonal distress, reflective functioning, and attachment insecurity; and significantly lower defensive functioning among women with BED compared to normal weight women without BED. The DMRS is reliable and valid when rated from AAI transcripts. BED is associated with lower defensive functioning. Further research on defensive functioning in BED may lead to better treatment outcomes.