Blood transfusion is a vital part of modern medicine. It is necessary to replace acute blood loss following an injury or in the course of a surgical operation. To treat severe anemia for instance when individuals cannot make blood for themselves. A quantitative research approach was conducted to determine the effectiveness of structured teaching program on knowledge regarding blood transfusion and its complications among 3rd year GNM students in selected schools at Hassan. by using one group of pre-test and post-test research design. 60 3rdyear GNM students were selected non-probability convenient sampling technique method. The pretest knowledge score was 39.89 % and mean score is 13.86 % and posttest knowledge score was 81.40 % and the mean score is 28.83%and enhancement mean were 41.51%. The paired t- value [t=52.85 DF=59] hence there is a significant difference between pretest and posttest knowledge score regardingblood transfusion and its complications among 3rd year GNM students in selected schools at Hassan. The significance was measured at 0.05 level. There was a significant association between the age of the students and no significant association between gender, religion, place of residence, educational status, previous information regarding blood transfusion and its complications, and source of knowledge in the pretest knowledge related toblood transfusion and its complications.