IN BRIEF This study examined the relationship between patient commitment and A1C. Patients completed the Altarum Consumer Engagement (ACE) measure. Multiple A1C values were extracted from medical records for 273 military beneficiaries. Effects were analyzed with generalized linear models. The ACE Commitment subscale was significantly inversely related to A1C trends. Low-commitment patients were more likely to have a high A1C. High-commitment patients were 16% more likely to have an A1C <7.0%; this likelihood increased to 65% over time. The ACE Commitment domain may be a useful clinical tool. Increasing patients' commitment to managing diabetes may improve their A1C over time.