Objectives: The objective was to determine if emergency department (ED) patients with diabetes mellitus (DM) who have primary care providers (PCPs) have better control of their DM than patients with no PCPs. Methods: This was a prospective, cross-sectional, observation study at a large, adult, urban, academic ED with 85,000 annual visits. ED patients with a history of DM were eligible. Patients with severe systemic disease, diabetic ketoacidosis (DKA), sepsis, active steroid use, pregnancy, or cognitive impairment were excluded. Consenting patients had hemoglobin A1c (HgbA1c) analysis and completed a questionnaire regarding demographics, lifestyle, medication usage, educational level attained, and health care access, including whether or not they had PCPs. HgbA1c levels were compared between subjects with and without PCPs using medians with interquartile ranges (IQRs). A continuous plot was developed to demonstrate the proportion of patients without PCPs (PCP)) compared to those with PCPs (PCP+) at every level of %HgbA1c across the entire measured range. Multivariate logistic regression analysis was used to determine which clinical and demographic factors obtained from the questionnaire were associated with improved glycemic control (increased relative risk [RR] of having a %HgbA1c < 8%). Results: A total of 284 patients were screened; 227 were enrolled, had HgbA1c analysis performed, and had complete PCP, race, and sex information. Complete demographic data (insurance status, employment status, etc.) were available on 209 subjects. Sixty-four of the 227 patients (28.2%) denied having PCPs. Median HgbA1c was 7.7% (IQR = 6.5% to 9.68%) in PCP+ versus 8.9% (IQR = 6.8% to 11.3%) in PCP) patients (p = 0.01). Ninety-one of 163 (55.8%) PCP+ subjects had a median HgbA1c < 8% versus 25 of 64 (39.1%) in the PCP) group (p = 0.02). After adjusting for multiple clinical and demographic variables, having a PCP remained significantly associated with a median HgbA1c value less than 8% (RR = 1.43; p = 0.04). Conclusions: Diabetes control was significantly better in patients with PCPs, even after adjusting for a number of potentially confounding social and demographic factors.