The screening of blood donors, which consists of a questionnaire and a pre-donation interview, helps identify and exclude donors who may pose a risk of transfusion-transmissible infections. Understanding the reasons for non-compliance—that is, failure to meet screening criteria—is essential for maintaining a high level of viral safety in blood products. An anonymous survey called Complidon was conducted online from September to December 2017 among a sample of blood donors. The data collected were adjusted to be representative of all individuals who donated blood between July 2016 and December 2017. Of the 420,190 donors surveyed, 108,386 responded to the questionnaire (26%). Overall non-compliance was estimated at 5.6%. The criteria least frequently met concerned having had more than one sexual partner in the past four months, either for the donor (1.9%) or for their partner (1%), travel-related criteria (1.2%), and sexual intercourse between men in the past 12 months (0.73% of men). The reasons for non-compliance differed depending on the type of contraindication. Donors who did not meet the criteria related to sexual activity were more likely to report not wanting to be excluded or to find the questions too personal. Donors who did not comply with criteria regarding travel or health more often reported having discussed these issues during the pre-donation interview and having been authorized to donate. Although non-compliance with blood donation selection criteria is relatively low in France, it still poses a risk to transfusion safety. This is why it is essential to ensure effective communication with donors so that they understand the rationale behind each contraindication and the need for honest answers, and to emphasize to healthcare professionals conducting pre-donation interviews the importance of attentive and empathetic listening.