Introduction: Colorectal Cancer (CRC) is the third most common cancer in the world. The risk of suffering from colorectal cancer in the first degree relatives is two to eight times higher than the ordinary people of the society. Therefore, the aim of this study is to evaluate the knowledge of the first degree relatives of the clients regarding the risk factors and signs of colorectal cancer and colonoscopy screening tests. Methodology: The present study was a descriptive cross-sectional study. In this study, 116 of the first degree relatives of patients were selected through simple random sampling. A researcher-made questionnaire was utilized to collect information about warning signs and risk factors. The reliability with Cronbach's alpha coefficient (α= 0.70) was calculated and then face and content validity were assessed by the professors. Data analysis was performed using SPSS software version 23 and using descriptive statistics (mean, and standard deviation) and inferential statistics (T-test and ANOVA). Results: The level of samples' knowledge about the risk signs of colorectal cancer was higher than the mean level (36.15 ± 8.46). The highest level of awareness about their (positive / negative) effects on colorectal cancer was related to consumption of vegetables, fruits (2.82 ± 0.65), and Aspirin consumption (1.34 ± 0.62). There wasn't a statistically significant difference between age, gender and education with the level of awareness of first degree of relatives but there was significant difference between the occupation of people and the level of awareness (P=0/005). The level of awareness of first degree of relatives about colonoscopy test was above the average level. (24.65 ± 4.57). The most knowledge about the nature of colonoscopy (2.78 ± 0.52) and the least awareness about the vitality of the operation were reported of the people above 50 (1.76 ± 0.74). There wasn't a statistically significant difference between the level of awareness of performing the colonoscopy and demographic characteristics of gender, age, education, and occupation. Conclusion: It is necessary to use new methods and strategies to maintain the available status and to raise the awareness of all people in the community regarding the signs and symptoms, especially the use of colorectal cancer screening to manage the initial programs of prevention and treatment.