Background: Colorectal cancer (CRC) is the third most prevalent malignancy in Iran. Although adequate knowledge about CRC and screening tests has a significant effect on screening behavior, there is still no clear information in this regard in Iran. The aim of the study was therefore to identify knowledge toward CRC and obstacles to screening tests among an Iranian population. Methods: We conducted a preliminary analysis with baseline data drawn from an ongoing randomized community trial among people aged 50 years and over in municipal district 6 in Tehran. A total of 360 members of health houses, who were not being exposed to CRC screening tests, completed the baseline survey and randomized to two study groups. Data were collected via personal interviews by 12 trained interviewers for demographics, knowledge related to CRC, and barriers to screening tests. Results: The mean age was 58.0 (±7.13) ranging from 50 to 86 years; 69% were female, 52% were unemployed, 65% had completed high school, and 90% had medical insurance. A considerable number of respondents stated that they had never heard about fecal occult blood test (61%) and colonoscopy (51%) as CRC screening tests. In general, participants were more likely to respond the knowledge items inaccurately. Four commonly stated reasons for not being screened were “absence of clinical symptoms” (29%); “doctor did not recommend the test” (26%); “never think of the test” (22%); and “did not think it was needed” (11%). Conclusion: Our findings indicated that lack of knowledge about CRC and various barriers to screening tests exist among Iranians. Our results may facilitate the development of effective educational strategies primarily aimed at high-risk people.