Abstract Study question Does unsuccessful egg sharing treatment impact on the egg share donor’s psychological well-being or make her regret her decision to participate? Summary answer Egg share (ES) donors whose treatment was unsuccessful did not regret egg sharing, and were unanimously happy for their recipient if her treatment was successful. What is known already ES programmes are a unique form of egg donation for two main reasons. First, both the donor and her anonymously matched recipient are engaged in the simultaneous pursuit of having a baby. Second, egg sharing schemes offer a benefit for the donor other than altruism. However, a major concern is for the psychological well-being of ES donors whose own treatment is not successful. This concern raised was based on opinion, rather than empirical research. It is therefore vital that the psychological well-being of ES donors through egg sharing is better studied. Study design, size, duration Data for this study were gathered using a questionnaire. Selection criteria for the study were those who had participated in egg donation treatment between 2014-2022 at Lister Fertility Clinic (LFC), Chelsea, London. Only patients who had agreed to participate in research during the consenting process of their treatment were sent an email invitation asking them to participate in the study. 394 ES donors were sent an email invite. Participants/materials, setting, methods After receiving the email link, respondents filled out the questionnaire online using the Qualtrics survey tool. The paper copies received were manually inputted by the research team onto Qualtrics. The questionnaire took on average 15-20 minutes for participants to complete. 197 egg share donors were included in analysis Statistical analysis was conducted using the χ², analysis of variance (ANOVA), Mann Whitney U test, and Fisher’s exact test. Main results and the role of chance This is the largest study to investigate the psychological issue surrounding ES donation. Overall, ES donors rated their treatment ‘very positively’ (85.7%). The vast majority of egg sharers (91.8%) were glad they took part in the programme. Significantly, patients were stratified into whether IVF treatment was successful or not, with successful treatment being defined as a resulting live birth. For egg sharers, there was no difference between positive or negative treatment outcome, and their responses to whether they: would participate in egg sharing again in the future; would recommend egg sharing to a friend or family member who needs fertility treatment; felt well informed of egg sharing; and felt they had sufficient support from the fertility clinic during and after treatment. The only answer that was statistically significant based on treatment outcome was when asked if they were ‘glad they took part’, with 99.4% of successful egg sharers answering yes, compared to 72.7% of unsuccessful egg sharers (Fishers exact, p < 0.05). Of the unsuccessful ES donors who found out their recipient’s treatment was successful, 100% reported they were ‘happy for their recipients’, with the vast majority of this category stating they were glad they took part (85.7%). Limitations, reasons for caution As with all questionnaire generated data, there is a potential for sampling bias. Second, this is a single centre study. LFC is one of the largest ES centres in the UK and has success rates above the national average. Therefore, this data may not represent the ES programme nationally. Wider implications of the findings As with all questionnaire generated data, there is a potential for sampling bias. Second, this is a single centre study. LFC is one of the largest ES centres in the UK and has success rates above the national average. Therefore, this data may not represent the ES programme nationally. Trial registration number n/a