Many adults with diabetes have family or friend ‘supporters’ involved in their care. Adult-supporter dyads were recruited to a trial comparing usual care to a 12-month program to engage and train supporters. Potentially eligible patients with T2DM and either HbA1c>8% or high systolic BP were identified via medical records. Patients randomized to the program received biweekly automated calls prompting reports on diabetes status, with tailored feedback to patients and supporters. Before primary care appointments, health coaches conducted a ‘visit prep call’ to improve dyad engagement in the visit. We examined patient characteristics predicting enrollment, and patient, supporter, and call characteristics predicting visit prep and automated call completion via separate multi-level regression models. Of 1119 contacted, 239 dyads (21%) enrolled. Patient predictors of enrollment included younger age (M=60y enrolled vs. 62 not, p <.01), and reason qualifying (BP+HbA1c criteria 30% enrolled, HbA1c only 22%, BP only 16%, p<.01). Of 123 dyads randomized to the program, 87 completed 12 months, and 32 are still enrolled. For 328 eligible visits, patients with high school-only education (AOR=5.7 vs. college degree, p<.01) and higher baseline SBP (AOR=1.2 per 10mmHg, p=.04) were more likely to complete prep calls. Among 2465 eligible automated calls, patients were more likely to complete calls if they had high satisfaction with their primary care team (AOR 1.4, p=.03). Those with higher baseline HbA1c (AOR 0.75, p=.06) trended towards less call completion. Patient insulin use, health literacy, patient activation, and diabetes distress did not predict completion of either type of call. In conclusion, high BP predicted enrollment and engagement in a dyadic-based diabetes program more than high HbA1c. Programs emphasizing the importance of BP in preventing diabetes complications may increase participant engagement. Disclosure S.C. Stoll: None. J. Piette: None. R.B. Trivedi: None. A.A. Lee: None. D. Obrosky: None. M.K. Mor: Stock/Shareholder; Spouse/Partner; AbbVie Inc. M. Heisler: None. A. Rosland: None. Funding U.S. Department of Veterans Affairs (IIR 14–074-1); Michigan Center for Diabetes Translational Research (NIDDK5P60-DK09292); Michigan Claude D. Pepper Older Americans Independence Center (NIA AG-024824)