Background The number of people with diabetes is estimated to increase to 642 million by 2040, with most having type 2 diabetes. Patients with diabetes require continuous monitoring and possible treatment changes. Patient education is the process of enabling individuals to make informed decisions about their personal health-related behaviours and internet-enabled interventions have the potential to provide support and information to patients with diabetes. Objective The aim of the study was to design a portal prototype based onto two models of care and a contextualised education programme to support the self-management of diabetes patients by involving stakeholders in the Iranian province of Razavi-Khorasan. Methods A Design-Based Research framework was adopted. A qualitative research method was used to analyse interviews with patients and care givers. Mock-ups were developed first and designed with features of user-driven and self-care models of care. The mock-ups also had adaptation features, such as for control of the disease, ability to cure self, and family support. The portal prototype was developed iteratively by building on the mock-ups and evaluated through interviews. The features and elements of the mock-ups and the portal prototype were evaluated in an outpatient diabetes clinic in Mashhad. Results Thirty-three participants were involved in the study. The evaluation of the mock-ups resulted in two themes and seven categories: 1) self-care improvement, including self-care requirements and self-management, and 2) educational usefulness, including medical information, information mode, mobility, interaction, and efficiency. The mock-up evaluation was used as a basis for designing a portal prototype. Next, the portal prototype was evaluated, and three categories emerged from the interview data: 1) user experience, 2) functionality, and 3) interactivity. Participants were not able to prioritise between the two care models. Some functionalities of the portal could benefit from the development within a cultural context to determine differences to the best way to present material. Conclusions A portal prototype has been designed to include two care models to support self-management and functionalities that support aspects of culture-specific diabetes self-care. This study provides guidance on developing an internet-enabled educational portal, aimed at providing support for patients in their social context.