Background: Delivering self-management support to people with T2DM is essential to reduce the health system burden and to empower people with the skills, knowledge and confidence needed to take an active role in managing their own health. Objective: This study aimed to evaluate the adoption, use and effectiveness of the My Diabetes Coach (MDC) program, an app-based interactive embodied conversational agent ‘Laura’, designed to support diabetes self-management in the home setting over 12 months. Methods: This hybrid effectiveness-implementation trial includes a randomized controlled trial. Adults with type 2 diabetes in Australia were recruited and randomized to the intervention arm (MDC) or the control arm (usual care). Program use was tracked over 12 months. Co-primary outcomes included changes in HbA1c and health-related quality of life (HRQoL). Data were assessed at baseline, 6 and 12 months and analyzed using linear mixed-effects regression models. Results: 187 adults with type 2 diabetes (57+10 years old, 42% women) were recruited and randomly allocated to intervention (n=93) and control (n=94). MDC program users (92/93 participants) completed 1,942 chats with ‘Laura’, averaging 243 minutes (SD: 212) per person over 12 months. Compared to baseline, mean estimated HbA1c decreased in both arms at 12 months (intervention: 0.33%, control: 0.20%), but there was no between-arm difference (-0.04%, 95% CI: -0.45, 0.36, p=0.834). At 12 months, HRQoL utility scores improved in the intervention arm, compared to the control arm (between-arm difference: 0.04, 95% CI:0.00, 0.07, p=0.039). Conclusions: The MDC program was successfully adopted and used by individuals with type 2 diabetes and significantly improved users’ HRQoL. These findings suggest the potential for wider implementation of technology-enabled conversation-based programs for supporting diabetes self-management. Future studies need to focus on strategies to maintain program usage and HbA1c improvement. Clinical Trial: The trial was registered before the start of recruitment in the Australia New Zealand Clinical Trials Registry ID ACTRN12614001229662.