Adults with type 2 diabetes (T2DM) and low socioeconomic status (SES) have high rates of medication nonadherence, and, in turn, suboptimal glycemic control (hemoglobin A1c [HbA1c]). We tested the initial efficacy of a short message service (SMS) text messaging and interactive voice response (IVR) intervention to promote adherence among this high-risk group. Eighty low SES, diverse adults with T2DM used the MEssaging for Diabetes (MED) SMS/IVR intervention for three months. We used a pre-post single group design to explore adherence changes over three months, and a quasi-experimental design to test the impact of MED on HbA1c among the intervention group relative to a matched, archival control group. Compared to baseline, adherence improved at one (AOR: 3.88, 95% CI: 1.79, 10.86) and at two months (AOR: 3.76, 95% CI: 1.75, 17.44), but not at three months. HbA1c remained stable, with no differences at three months between the intervention group and the control group. MED had a positive, short-term impact on adherence, which did not translate to improvements in HbA1c. Future research should explore the longer-term impact of SMS/IVR interventions on the medication adherence of high risk adults with T2DM.