Background: Digital educational technologies in health have been an important instrument for promoting learning, self-care, self-esteem, and security regarding prevention and health promotion actions that lead to changes in behavior, mainly for non-communicable disease patients, such as type 2 Diabetes Mellitus (DM 2). Objective: This study aimed to describe a protocol for evaluating the effect of an app for cell phones and tablets on the blood glucose of older adults with DM 2. Methods: The protocol will be used to compare the effectiveness of an application for mobile devices concerning the educational booklet in reducing Glycated Hemoglobin in older adults with DM 2 in Primary Health Care. This protocol is part of a Randomized Clinical Trial project entitled Effectiveness of a Mobile Device Application on Glycated Hemoglobin in Elderly People with Type 2 Diabetes Mellitus: a Randomized Clinical Trial. Results: The protocol was structured in the following phases: (i) sample calculation, (ii) invitation to participate in the study according to the eligibility criteria; (iii) participant registration; (iv) randomization and allocation of participants into groups (double blinding); (v) application of the intervention; (vi) post-intervention procedures (post-test); (vii) data analysis. Conclusion: It is expected that encouraging studies on the impact of a mobile application will improve and enhance health education focused on self-care for older adults with DM 2, potentially influencing the local health system by reducing hospitalizations due to conditions that are sensitive to primary care, since health promotion and prevention of DM-related illnesses will be the main focus of the application and booklet developed.