Background: It has been suggested that patients’ knowledge is very essential to improve the outcomes of diabetes. Therefore, this study aimed to determine the impact of the intervention program on the patient’s knowledge of T2DM and HbA1c. Methods: This was an interventional study, which was carried out in the diabetic clinic in a governmental hospital at King Saud Hospital, Unaizah city, in Saudi Arabia, for eight months, starting from June 2017. One hundred and two patients were selected to be included in this study. Michigan Diabetes Knowledge Test (MDKT) was used to assess knowledge. Results: There was a significant improvement in the overall program although individuals responded differently to each item. Patients’ knowledge scores significantly (p=0.001) increased after the intervention program from 9.05±1.92 to 12.29±1.00. The level of patient’s knowledge before the intervention found 4.9% was low level, 70.6% was moderate, and 24.5% was high. In contrast, the level of patient’s knowledge after intervention found 4.9% was moderate level, and 95.1 was high level. The difference between the patient knowledge post-test and the comorbidities of the patient was not significant p> 0.05. Conclusion: The intervention program has improved knowledge among elderly patients with T2DM. The improvement in knowledge suggests important roles of the pharmacist in the patient’s health management process. There is a need for a complete understanding of diabetes by the patients to improve management and to address problems such as lack of awareness, self-care, and knowledge.