Background: Cancer is one of the most common causes of death in Turkey. Nurses are essential providers of preventive care for patients, especially breast, cervical and colorectal cancer screening as part of routine preventive practice. The aim of this study was to assess knowledge of these cancers among nurses in Karabuk State Hospital. Materials and Methods: This cross-sectional and descriptive study was performed from April 1 to July 30, 2013. The study sample consisted of 226 nurses working in Karabuk State Hospital. Results: Mean age of the nurses was $32.07{pm}8.39$. 62.4% of nurses practiced breast self examination when they remembered it, while 39.8% of them did not take a Pap smear test since they did not think it was necessary. 64.2% of nurses would like to receive information about cancer and screening tests. Majority of them had given true answers to questions on breast, cervical and colorectal cancer. There were significant relationships between cancer knowledge scores and marital status, working experience, and level of education. Conclusions: Nurses possess adequate knowledge about breast cancer but they need more information on cancer risk estimation. Awareness may be raised in nurses by establishing continuing education programs regarding the risk factors, symptoms, protection methods, early diagnosis, and scanning of breast, cervix and colon cancers.