Stress is associated with higher blood glucose in patients with diabetes, but the strength of this association varies considerably across patients. The current daily diary study of 129 patients with type 2 diabetes examined whether individual differences in emotional stress reactivity were associated with fasting blood glucose and whether emotional support provided by spouses moderated this association. Greater stress reactivity was related to greater variability in patients’ fasting glucose readings and, among patients with less support, to higher fasting glucose levels. Investigating individual differences in emotional stress reactivity may help to clarify the role of stress in blood glucose control.