Marriage can enhance health for individuals with a chronic disease, yet spouses may also undermine disease management. The current study investigated spousal undermining of dietary regimen in 129 patients with type 2 diabetes mellitus. A total of 40 patients reported that their spouses tempted them with forbidden foods, and 15 reported that their spouses conveyed disregard for their diabetic diet. Spousal tempting was associated with worse dietary adherence, and spousal disregard with worse nondietary adherence. Spousal undermining is relatively rare but is associated with patients’ disease management and warrants further investigation to better understand how spouses influence partners’ day-to-day management of chronic diseases.