Background: Colorectal cancer (CRC) screening has been shown to reduce CRC incidence and mortality. Several CRC screening modalities are guideline recommended for average-risk adults aged 45-75 years. CRC screening is underutilized in the US and access to facility-based options, such as colonoscopy, represents a potential barrier. Home-based stool tests are guideline-endorsed and offer a convenient, accessible, scalable option for CRC screening. Thus, understanding the factors that influence completion of stool-based CRC screening is important to guide interventions to improve adherence. We developed a survey, informed by behavioral theory, to identify psychosocial, behavioral and communication factors associated with completion of mt-sDNA screening. Methods: The survey instrument was finalized through expert review, quality testing, and cognitive testing. Adults aged 45-75 years, with a US postal address, who received a valid order for mt-sDNA and whose kit was shipped between 5/21-9/21 were eligible for sampling. RTI administered the survey between 3/22-6/22. Participants had the option to complete electronic or paper surveys. We fit a multivariable logistic regression to identify factors significantly associated with mt-sDNA test completion. Results: Of 17,370 individuals invited to participate, 2,973 completed the survey (AAPOR RR3 = 21.7%); 77.3% of the sample completed the mt-sDNA test. Responders and non-responders did not differ significantly by sex or age. Controlling for demographic characteristics and insurance status, the odds of mt-sDNA test completion were significantly higher among participants who reported greater perceived test effectiveness (OR = 1.20), greater ease (OR = 4.06), and greater comfort in test use (OR = 1.18). Odds of test completion were significantly higher among participants who reported their healthcare provider discussed the mt-sDNA test with them (OR = 2.01) and involved them a great deal in decision making about CRC screening (OR = 1.29). Participants who expressed greater worry about developing CRC were less likely to return their mt-sDNA kit (OR = 0.81). Conclusions: To improve population adherence to CRC screening recommendations, efforts are needed to ensure patients understand the attributes and effectiveness of available test options and feel adequately prepared to complete their preferred screening test. Additionally, healthcare providers must be appropriately prepared and resourced to educate and to engage patients in shared decision-making about CRC screening.