This cross-sectional descriptive study was carried out among 75 oral cancer patients at National Institute of Cancer Research and Hospital, Dhaka, from July 2013 to December 2013, to assess the level of knowledge of oral cancer patients about of oral cancer. The mean age of the respondents was 45.50 years of then 61.33% were male and 38.67% were female. In this present study it was found that 80% had no knowledge about common causes of oral cancer. Common age of oral cancer occurrence could answer correctly and by 42.67% had no knowledge about it. Effects of smoking were correctly answered by 66.67%. Regarding effects of betel leaf and associated ingredients 6.67% respondents answered correctly. Only 1.33% respondent correctly answered about effects of alcohol consumption. But 60% respondents correctly answered about effects of chronic oral ulcer and effects of chronic oral infectious diseases. Regarding effects of poor oral hygiene and foods mixed up with chemicals (preservatives, insecticides and pesticides) only 33.33% respondents answered correctly. About effects of fewer intakes of fruits and vegetables, 8% respondents answered correctly. Effects of excess intake of red meat and positive family history could not be correctly by 100%. Finally, the study revealed that the knowledge of oral cancer patients about of oral cancer was poor, and need to improve the situation through health education.