Background and Objectives: Previous work has studied barriers to donating blood or plasma among current, lapsed and non-donors. Still, it remains unclear why donors stop donating and end their donor career voluntarily. A thorough understanding of why donors stop is necessary to develop more effective retention strategies and manage the decline in whole-blood donors. Methods: An online questionnaire that contained questions about reasons to stop donation was sent out to 7098 Dutch whole-blood donors who deregistered from the donor pool in 2015 but who were not permanently deferred for medical reasons (response: N = 2490, 35%). Results: The final sample consisted of 1865 stopped blood donors. Of the stopped blood donors, 28·4% reported that negative physical experiences were (partly) the reason to stop. This stopping reason was more often reported by women than men, those aged 19–33 years compared to older groups and those who had donated five times or less compared to those with more donations. Inconvenient opening times (26·1%) was a stopping reason more frequently reported by men compared to women, those aged 34–50 years compared to their younger and older counterparts and those who had donated more than five times. Conclusions: We found that the stopping reasons for blood donors are dependent on gender, age and the number of donations. Stopping reasons differ substantially from barriers experienced by current, lapsed and non-donors. More research on preventing negative physical experiences and implementing more flexible opening hours are advised.