Blood transfusion is a medical procedure that is designed to provide patients who need blood or blood products to correct a defect. Secure supply of safe blood components, based on voluntary, non-remunerated blood donation is an important national goal to prevent blood shortages. Now a day, in many low and middle income countries, blood supply is critically inadequate. Therefore, the objective of this study was to assess knowledge, attitude, and practice of voluntary blood donation and associated factors among adults of Birbir town. Community based cross sectional study design was employed among residents of Birbir town with 387 samples from July 1 to July 30, 2016. After proportional allocation to size to each of 4 villages, systematic sampling method was used to select households. Data was collected from all villages by investigators using standard questionnaire. Finally data was entered and analyzed using SPSS version 20 software. About 144(38.3%), 170(45.2%) and 40(10.6%) of respondents have adequate knowledge, favorable attitude and donated blood respectively. Educational status and occupation were determinants of knowledge, age and knowledge were determinants of attitude and attitude was the only determinant of practice of voluntary blood donation. This study revealed that the prevalence of knowledge, attitude and practice of voluntary blood donation is low. There is a need to design and implement awareness creation program on blood donation. Offices of blood banks in the country, health offices and other stake holders should organize educational campaigns to build community awareness, positive attitude and boost voluntary blood donation among the communities.