Background. People with diabetes are at high risk for shoulder pain, limited joint mobility, and adhesive capsulitis. Objective. The objective of this study was to evaluate the effects of a shoulder movement intervention (ShoMo) compared to a wellness intervention on the primary outcomes of active shoulder flexion and reported Shoulder Pain and Disability Index (SPADI) measured after intervention and 9 months later. Design. The design was a prospective, randomized, controlled clinical trial. Setting. The setting was a research center at an academic medical center. Participants. Fifty-two participants with type 2 diabetes and shoulder pain or limited motion were randomized to a group receiving ShoMo (N = 27; mean age = 59.3; SD = 7.0) or a group receiving wellness activities (N = 25; mean age = 57.9; SD = 7.7). Intervention. The ShoMo group received instruction in a progressive, active shoulder movement program. The wellness group received instruction in diabetes management. Measurements. Measurements were made at baseline, after 3 months of intervention, and at 6, 9, and 12 months after baseline. Results. After intervention, the ShoMo group had a 7.2-degree increase in active shoulder flexion compared with the wellness group (95% CI = 0.9-13.5°), but there was no difference at subsequent follow-ups. The ShoMo group showed a 12.7-point improvement in the SPADI score compared to the wellness group after intervention (95% CI = 1.1-24.3), which remained better than the wellness group 9 months later. Limitations. The number of participants and duration of follow-up were inadequate to determine if intervention can help to prevent future severe shoulder problems. Conclusions. A progressive shoulder movement program can have meaningful effects on active motion and symptoms in people with type 2 diabetes and mild-to-moderate shoulder symptoms, with symptom improvement lasting at least 9 months.