Background of the study: Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body.The occurrence of cancer in India is 70–90 per 1, 00,000 population and prevalence is estimated around 25, 00,000 (2.5 million). As per WHO in 2012, 4.77 lakh man and 5.37 lakh women died due to cancer in India.Colorectal cancer is third most common cancer among men (663000 cases, 10% of total cases) and second in women (570000 cases, 9.4% of the total cases) worldwide.  The colorectal cancer is preventable if it detected for its early sign and symptoms.  Aim: Aim of the study was to assess effectiveness of health education regarding prevention of colorectal cancer among patients.Material and method: An evaluatory research approach with quasi experimental non randomized control group design was used. The Sampling technique was purposive sampling. Data was collected by using structured knowledge questionnaire. The data was tabulated and analyzed in term of objectives of the study using descriptive and inferential statistics.Results: In experimental group mean post test score (18.06) was higher than mean pre test score (8.77). In control group mean post test score (9.3) was similar to mean pre test score (8.13). Unpaired t– test value 7.28 and mean difference 31.31 suggesting marked difference between knowledge score of control and experimental group. The chi–square value shows that there is a significant association between knowledge of patients with selected demographic variable such as age, occupation, food pattern and living area. There is no significant association betweengender, educational status, family history of colorectal cancer, previous knowledge and life style. Conclusion:The study finding revealed that health education was effective in improving knowledge of patients.