We sought to investigate intentions to undergo primary screening with colonoscopy in an attempt to predict future colorectal cancer screening behaviors and the feasibility of implementing colonoscopy as the primary screening modality for colorectal cancer in the National Cancer Screening Program (NCSP) of Korea. Data were obtained from a nationwide online survey conducted in 2018. The survey included a total of 800 eligible adults aged over 45 years. Study measures included the history of screening colonoscopy within the past 10 years and intentions to undergo primary screening with colonoscopy under the NCSP based on the five constructs of the Health Belief Model. Logistic regression analysis was conducted to examine factors associated with intentions to undergo primary screening with colonoscopy. Approximately 77% of the participants expressed strong willingness to undergo primary screening with colonoscopy under the NCSP. Higher perceived severity and perceived benefits were significantly associated with stronger intentions to undergo screening with colonoscopy (adjusted odds ratio aOR, 1.53; 95% confidence interval CI, 1.10-2.14 and aOR, 2.74; 95% CI, 1.76-4.28, respectively). Greater perceived barriers (aOR, 0.65; 95% CI, 0.45-0.93) were significantly associated with weaker intentions. Cues to action elicited the strongest screening intentions (aOR, 8.28; 95% CI, 5.23-13.12). The current study findings highlight the need for increasing awareness of the severity of CRC and the benefits of colonoscopy screening. Family-orientated recommendation strategies and reducing complications may boost an individual's intentions to undergo colonoscopy.