Background Posttraumatic stress disorder (PTSD) and anxiety disorders such as panic, generalized and social anxiety are highly prevalent among Veterans of all eras and negatively impact functioning and quality of life. Avoidance is a hallmark feature of anxiety and functions to maintain the disorder. Although cognitive behavior therapy (CBT) is effective, a significant proportion of Veterans show minimal improvement following treatment. This is often due to poor treatment adherence such as avoidance of using skills taught in CBT that require confronting distressing memories and feared situations. Avoidance behavior also can extend to caregivers and family members of Veterans, who may engage in accommodation behaviors (i.e., changing their own behaviors) to help alleviate distress experienced by their loved ones. As such, accommodation by family members undermines the effectiveness of CBT and is associated with greater symptom severity and functional impairment in persons with anxiety. Objectives This study will examine the feasibility, acceptability, and satisfaction associated with a new intervention for family members of Veterans undergoing CBT for anxiety-based disorders. Adjunctive Family-CBT (AF-CBT) provides family members psychoeducation on anxiety and teaches skills that can be used to facilitate the recovery of Veterans who are in the process of completing treatment for anxiety. Aims of the study are to: (1) adapt and refine AF-CBT through an iterative process that will be informed by feedback from Veterans and family members; (2) examine the feasibility and acceptability/satisfaction of AF-CBT; (3) assess the validity and reliability of the Family Accommodation Scale-Anxiety adapted for Veterans and family members; and (4) examine the associations between family accommodation behavior and readjustment and anxiety in Veterans. Methods The proposed study involves a total of 47 Veterans and family member dyads (V/F dyad) and will be conducted in two phases. In phase 1, 12 V/F dyads will be recruited, and family members will receive AF-CBT while the Veteran undergoes iCBT for anxiety. The intervention will be delivered in three separate cohorts (approximately 4 V/F dyad in each cohort). During the 1- month assessment, information obtained from qualitative interviews will be used to refine the intervention in an iterative process with each cohort. In phase 2, 35 V/F dyads will be recruited and administered the finalized version of AF-CBT following the same treatment and assessment format. Qualitative interviews will focus on each V/F dyad’s experience with the AF-CBT intervention and whether specific components of the intervention facilitated the Veteran’s recovery process.