Background: Non-communicable diseases (NCDs) and their risk factors are highly prevalent in Iran; thus there is an urgent need for nutrition interventional programs to curtail these risk factors. This study was aimed to assess knowledge, attitudes and practice of urban Tehranians regarding nutrition and in relation to non-communicable diseases.Materials and methods: This cross-sectional study, conducted within the framework of the second phase of Tehran Lipid and Glucose Study (TLGS). From 15005participants in TLGS, 826 subjects (457 women and 369 men), aged 20- 70 years old were randomly selected. Their knowledge, attitudes and practice were assessed by a questionnaire, the validity and reliability of which were determined and authenticated by focus groups and an expert panel. Height and weight were measured and body mass index (BMI) was calculated. Biochemical data including serum cholesterol, triglycerides and HDL cholesterol were measured according to standard protocols and LDL concentration was calculated. For determining the correlation of knowledge, attitudes and practice with sex, age and educational level, Chi-square test was used.Results: Of the studied population, 26.5, 52.7 and 20.8% had desirable, moderate and weak knowledge scores, respectively. For attitude, 27.6, 48.9 and 23.5% had desirable, moderate and weak score, respectively. Regarding practices the percentages for this group were 27.4, 51.7 and 20.9%, respectively. Those with middle school degree or university graduates had higher knowledge scores than illiterate and low literate ones (p<0.001). On the other hand, illiterate and low literate groups had higher practice score as compared to middle school and high school graduates (p<0.001). Mean practice scores of university graduates were higher than high school graduates (p<0.05). Married individuals had more desirable practices than singles (p<0.001).The difference disappeared after adjusting for age. Those aged 30-50 year old had higher knowledge scores than older ones (p<0.001). With increase in LDL cholesterol or total cholesterol level, people had more desirable practices (p<0.001). Subjects with borderline triglycerides level had better practice scores than normal individuals (p<0.001). Based on BMI, obese individuals had more desirable nutritional practices as compared to overweight and normal ones (p<0.001).Conclusion: The findings revealed that age, educational level, gender and matenal status are factors that can influence nutritional knowledge, attitude, and practice. It is vital to implement programs using different ways to promote the nutritional practices of the population.