Background: Diabetes mellitus has become a global epidemic with significant disability, premature death and enormous medical costs. According to Indian Heart Association 2016, reveals that, India is projected to be home to 109 million individuals with diabetes by 2035. It has been well established that data on knowledge on control of diabetes reveals aspects of education that need to be reinforced and addressed in order to improve diabetes control and management. Objectives: The objectives of the study is :– To assess the pretest knowledge regarding control of diabetes mellitus among diabetic clients, to assess the effectiveness of pocket reference regarding knowledge on control of diabetes among diabetic clients and to find the association between pretest knowledge score with selected variables. Material& Method: Diabetic clients were selected by convenient sampling technique from endocrinology ward and medicine wards who are taking treatment in this hospital who can read and write English and Assamese and available during the study. Diabetic clients who agreed to participate in the study were assessed by demographic proforma and self structured knowledge questionnaire. The collected data were analyzed by Statistical Package for the Social Science (SPSS) version 22. Result: 43 clients with diabetes mellitus participated in the study. Majority 27.9% were in the age group of 41–45 years, maximum 53.5% belongs to economic weaker group, working less than 8 hrs 58.1%, 65.1% does not have family history of diabetes. The mean of the post–test knowledge score 35.39 was higher than that of the pre–test knowledge score 12.20 with a difference of 23.19 significant at the (p=0.05). Conclusion: Diabetic clients seem to have less knowledge regarding control of diabetes. Keeping in view the findings of the present study, the following recommendation was made:  A vast education programme is necessary for all the clients to control the disease and prevent complication. On the basis of the findings, the researchers conclude that the pocket reference was effective in improving the knowledge regarding control of diabetes among diabetic clients.