Background The widespread access to medically assisted reproduction (MAR) techniques for all women, regardless of any infertility diagnosis, has led to an increased, but as yet unmet, demand for sperm donors in Portugal. For this study, we deployed an online survey to explore men's motivations for donating and their attitudes toward anonymity and donating for specific groups. Method The study's sample comprised men who were eligible to donate sperm (N = 282). The relationships between these factors and participants'psychological and sociodemographic characteristics were also explored. Results The results mostly indicated altruistic reasons for donating, positive attitudes toward anonymity, and a greater willingness to donate to infertile women. Overall, sexual orientation was not associated with the participants' attitudes and motivations. Age, education level, conscientiousness, empathic concern, and conservative and religious values were associated with the participants' motivations and attitudes toward sperm donation. Conclusion Recruitment campaigns should therefore consider the specific motivations, attitudes, and psychosocial characteristics of potential sperm donors. Indeed, parenthood is a universal right, so sperm donation should be encouraged, regardless of recipients' fertility status. Clear information about the identifiability of sperm donors should also be provided.