Introduction: Fecal occult blood tests are recommended for colorectal cancer (CRC) screening in Europe. Recently, the fecal immunochemical test (FIT) has come into use. Sociodemographic differences between participants and nonparticipants may be less pronounced when using FIT as there are no preceding dietary restrictions and only one specimen is required. The aim of this study was to examine the associations between sociodemographic characteristics and nonparticipation for both genders, with special emphasis on those who actively unsubscribe from the program. Methods: The study was a national, register-based, cross-sectional study among men and women randomized to be invited to participate in the prevalence round of the Danish CRC screening program between March 1 and December 31, 2014. Prevalence ratios (PRs) were used to quantify the association between sociodemographic characteristics and nonparticipation (including active nonparticipation). PRs were assessed using Poisson regression with robust error variance. Results: The likelihood of being a nonparticipant was highest in the younger part of the population; however, for women, the association across age groups was U-shaped. Female immigrants were more likely to be nonparticipants. Living alone, being on social welfare, and having lower income were factors that were associated with nonparticipation among both men and women. For both men and women, there was a U-shaped association between education and nonparticipation. For both men and women, the likelihood of active nonparticipation rose with age; it was lowest among non-western immigrants and highest among social welfare recipients. Conclusion: Social inequality in screening uptake was evident among both men and women in the Danish CRC screening program, even though the program is free of charge and the screening kit is based on FIT and mailed directly to the individuals. Interventions are needed to bridge this gap if CRC screening is to avoid aggravating existing inequalities in CRC-related morbidity and mortality.