We examined associations between numeracy and sociocognitive factors associated with colorectal cancer screening uptake (n = 964). Nearly half (45.7%) of the respondents incorrectly answered a numeracy question (low numeracy). Low numeracy respondents were less knowledgeable about colorectal cancer (p < .001), less positive towards screening (emotional, p < .001 and practical, p = .001) and less likely to intend to participate in screening (p = .001). They also reported greater defensive processing of cancer information (p = .001). Sociocognitive factors fully mediated the relationship between numeracy and screening intention. Addressing numeracy issues may reduce inequalities in CRC screening participation, but communication strategies could be limited by the tendency process cancer information defensively.