Aims Although colorectal cancer screening (CRC) using stool-based test is well-studied, evidence on fecal immunochemical test (FIT) patterns in a safety-net healthcare system utilizing opportunistic screening is limited. We studied the FIT completion rates and adenoma detection rate (ADR) of positive FIT-colonoscopy (FIT-C) in an urban safety-net system. Methods We performed a retrospective cross-sectional chart review on individuals >= 50 years who underwent CRC screening using FIT or screening colonoscopy, 09/01/2017-08/30/2018. Demographic differences in FIT completion were studied; ADR of FIT-C was compared to that of screening colonoscopy. Results Among 13,427 individuals with FIT ordered, 7248 (54%) completed the stool test and 230 (48%) followed up a positive FIT with colonoscopy. Increasing age (OR 1.01, CI 1.01-1.02), non-Hispanic Blacks (OR 0.87, CI 0.80-0.95,p = 0.002), current smokers (OR 0.84, CI 0.77-0.92,p < 0.0001), those with Medicaid (OR 0.86, CI 0.77-0.96,p = 0.006), commercial insurance (OR 0.85, CI 0.78-0.94,p = 0.002), CCI score >= 3 (OR 0.82, CI 0.74-0.91,p < 0.0001), orders by family medicine providers (OR 0.87, CI 0.81-0.94,p < 0.0001) were associated with lower completion of stool test. Individuals from low median household income cities had lower follow-up of positive FIT, OR 0.43, CI 0.21-0.86,p = 0.017. ADR of FIT-C was higher than that of screening colonoscopy. Conclusion Adherence to CRC screening is low in safety-net systems employing opportunistic screening. Understanding demographic differences may allow providers to formulate targeted strategies in high-risk vulnerable groups.