To determine whether anxiety is associated with poor glycemic control in adults with type 1 or type 2 diabetes. MEDLINE, PubMed, and PsycINFO databases were used to locate studies that measured the association of anxiety with glycemic control. Meta-analytic procedures were used to convert the findings to a common metric, compute effect sizes (ES), and statistically analyze the collective data. The search procedures identified 12 studies, 11 (92 percent) of which satisfied the criteria for inclusion in the meta-analysis. In this overall group, anxiety was not associated with glycemic control (p = 0.19), although the ES was marginally statistically significant (ES = .09, 95 percent CI = 0.04 to 0.14). In studies that determined anxiety from diagnostic interviews, anxiety was associated with hyperglycemia (p = 0.003) and the ES was also statistically significant (ES: 0.25, 95 percent CI = 0.10 to 0.38). The existing literature suggests that anxiety disorders are associated with hyperglycemia in diabetic patients. Additional studies are required to confirm the magnitude of the relationship, to elucidate moderating and causal factors, and to determine whether successful treatment of anxiety improves glycemic control.