Diabetes Mellitus has become a health problem of great magnitude recently. If it is untreated, it is leading to many complications silently. Diabetes self management is the corner stone for controlling Diabetes and preventing Diabetes complication. The aim of the study was to assess the effectiveness of demonstration on self care management among Clients with diabetes mellitus. The self care management includes practice of regular blood sugar level monitoring and self administration of insulin injection among client with diabetes mellitus. In quasi experimental research design one group pre and post test design was used. Totally 75 Clients with diabetes mellitus were selected by using purposive sampling method. Assessing the level of knowledge on self blood glucose monitoring and self insulin injection administration among clients with diabetes mellitus in pretest, 87% and 93% had inadequate knowledge respectively and it was reduced to 12% and 8% in post test. Regarding the demonstration of self blood sugar monitoring and self insulin injection administration practice 97% and 98% had poor practice in pretest and it was reduced to 22% and 27% in post test respectively. There was significant association between the level of knowledge with the selected demographic variables such as age, education and source of health information at P< 0.005. The study concluded that there is effectiveness of demonstration on self care management among Clients with diabetes mellitus.