Colorectal cancer represents a significant health threat worldwide. First-degree relatives (FDRs) of colorectal cancer patients are at increased risk of developing the disease. There is a need to understand the psychosocial predictors of screening uptake in this group. An extended theory of planned behavior (TPB) that included perceived risk was employed to do this. Telephone interviews were conducted with 110 FDRs. The TPB accounted for up to 51% and between 16% and 25% of the variance in intention and behavior, respectively. Injunctive norm emerged as the strongest predictor of screening intention. Therefore, it is recommended that interventions to maximize screening uptake target this variable in particular.