Most patients with diabetes do not meet all evidence-based goals of care, and many patients report poor communication and lack of involvement in decision-making during primary care visits. To test the hypothesis that a “Pre-Visit Prioritization” secure email message could improve visit communication and glycemic control among patients with type 2 diabetes. We conducted a pragmatic, provider-randomized, multi-site clinical trial from March 2015 to October 2016 across 30 primary care practices within Kaiser Permanente Northern California (KPNC), a large integrated care delivery system. Eligible patients had at least 1 year of KPNC membership, type 2 diabetes with most recently measured hemoglobin A1c (HbA1c)?>?=?8.0%, and were registered users of the KPNC online patient portal. Patients in the intervention arm, upon booking an appointment, received a secure email through the KPNC online portal with a link to the EHR allowing them to submit their top one or two priorities prior to the visit. Control patients received usual care. Glycemic control; change in HbA1c 6 and 12 months after the initial visit; patient-reported outcomes related to patient-provider communication and patient care experiences. During the study period, 1276 patients had at least one eligible visit. In post-visit surveys (n?=?457), more intervention arm patients reported preparing questions for their visit (72% vs 63%, p?=?0.048) and being given treatment choices to consider (81% vs 73%, p?=?0.041). Patients in both arms had similar reductions in HbA1c over the 12-month study period (0.56%?±?1.45%), with no significant differences between arms. A “light touch” email-based pre-visit intervention resulted in improved measures of visit interaction but did not significantly improve glycemic control relative to usual care. Improving diabetes clinical outcomes through more effective primary care visits may require more intensive approaches to patient visit preparation. NCT02375932.