Background: Around a third of patients with cancer report moderate to severe pain and with the development of metastases, the incidence of pain increases to 40% to 60% of patients, and in far advanced disease, 60% to 90% of patients report significant pain. Majority of health professionals found in Ethiopia do not know how to holistically assess and control pain and only insignificant numbers are familiar with the World Health Organization (WHO) pain management protocol. Hence, this study is conducted to assess knowledge of nurses regarding cancer pain management at selected health institutions, offering cancer treatment in Addis Ababa, Ethiopia, 2013.