Background: The usefulness of technology and the powerful capabilities of technological applications have led to a significantly increased interest in finding novel approaches to support older adults’ self-management. Self-management technological applications have been used in various contexts, and usability is key in sustainability and adoption of such technologies. Objective: The purpose of this research is to assess the usability of the ASSISTwell application in an older adult population with Diabetes Type II (DMII) and explore whether the application can effectively enhance DMII patients’ self-management. Design: Qualitative interviews, Observation, and Quasi-experimental design. Methods: Semi-structured interviews, observation, documentation, and quantitative standardized measures were used in this study. A purposive sample of 24 elderly patients with DMII was recruited for the study. Descriptive and inferential analysis were used to analyze the quantitative data. Simple content analysis was used to organize the emerging usability themes. Results: User feedback from the four-week user intervention demonstrated good usability of the ASSISTwell application. After using the ASSISTwell for 30 days, there was significant improvement in the perceived diabetes self-management skills of the intervention group (difference in mean PDSMS (F (1, 20) =5.11, p=0.035). Furthermore, those who used ASSISTwell (mean= 30.22, SD= 6.34) had higher PDSMS scores than those who received usual care without ASSISTwell (mean= 23.95, SD= 7.12). There was no significant difference in mean blood glucose levels (F (1, 20) =0.37, p=0.54) between the two groups. Those who used ASSISTwell (M=178, SD=40) had lower blood glucose levels than those who received usual care without ASSISTwell (M=185, SD=49), but the difference is not statistically significant. Conclusions: The novel ASSISTwell application presented in this paper helped participants improve their diabetes self-management skills. A well-designed application with new features has the ability to provide more promising results regarding improving perceived diabetes self-management skills. Also, examining usability is an essential step in application development to ensure that the application's features match users' expectations and needs and minimize the likelihood of user errors and difficulties using the system.