Abstract Study question Which motivations drive women to consider egg donation in Portugal, and how does the level of ambivalence play a role? Summary answer Higher motivation to help others and valuable genetics were associated with a lower ambivalence, while financial motivation was associated with a higher ambivalence towards donation. What is known already Egg donation has become a common treatment option for patients struggling with infertility. Therefore, understanding the egg donors decision-making process is crucial. Previous studies have shown that the motivations for egg donation are multifaceted and vary as a function of individual characteristics, such as motherhood and sexual orientation. Egg donors consistently report altruism as their main motivation for donation, but little is known about their ambivalence. Our aim was twofold: (1) to investigate the motivations of egg donors in Portugal; (2) to investigate and compare the levels of ambivalence towards egg donation in relation to the motivations and socio-demographic characteristics. Study design, size, duration Descriptive cross-sectional study conducted in two Portuguese Fertility Centers. Participants were 177 Portuguese women who demonstrated their intention to become egg donors through an online form (www.soudadora.pt). The candidates were invited by e-mail to participate in this study and informed consent was obtained prior to the data collection. The data were collected through an online questionnaire prior to the screening and donation process, between November 2023 and January 2024. Participants/materials, setting, methods Participants were 177 Portuguese women (Mage = 27.30, SD = 4.26). Motivations were measured through a self-report scale focusing on five dimensions: “to help others”, “empathy”, “valuable genetics“, “to procreate”, “financial compensation”. Ambivalence was measured through a self-report scale focusing on mixed feeling about the donation. Data analysis included descriptive and inferential methods to establish differences in motivations, as well as associations between participant's ambivalence, motivations, and socio-demographic characteristics. Main results and the role of chance The motivations with higher scores were to help others (M = 11.03, SD = 1.54; min. = 0, max. = 12) and valuable genetics (M = 3.62, SD = 0.75; min. = 0, max. = 4; all paired-sample t-test p < .001), while the financial compensation revealed the lowest scores (M = 3.48, SD = 1.83; min. = 0, max. = 8; all paired-sample t-test p < .001). The ambivalence levels towards donation were generally low (M = 2.58, SD = 1.74, min. = 0, max. = 7). A higher motivation to help others and valuable genetics were significantly associated with a lower ambivalence (r(175) = -0.18, p = .014; r(175) = -0.18, p = .020, respectively). On the other hand, a higher financial motivation was significantly associated with a higher ambivalence towards donation (r(175) = 0.21, p = .01). Moreover, the higher the number of children, the higher the womeńs empathic motivations (r(175) = 0.50, p < .001). Women who identified as homosexual/bisexual reported higher motivations to procreate, as compared to heterosexual women (t(161) = -2.84, p = .01). The educational level did not significantly influence either the motivations or ambivalence of the candidates to egg donation. Limitations, reasons for caution Relying on self-report questionnaires might have introduced bias (social desirability). Investigating whether the motivations and ambivalence of these women correlate with their inclusion on the donation program and with their post-donation satisfaction could provide valuable insights. Donor anonymity is a key aspect in the decision-making process which was not addressed. Wider implications of the findings Understanding egg donors’ motivations is pivotal for several aspects, such as maintaining ethical standards and predicting donation outcomes. Identifying and addressing ambivalence could contribute to improved donor well-being and a successful donation. Overall, understanding the decision-making process enables a more effective and personalized approach, benefiting both donors and recipients. Trial registration number Not applicable