Aim: To analyze the attitude of university nursing students at Spanish universities toward organ donation and transplantation and the factors affecting to their attitude. Background: The opinion of future nurses toward organ transplant donation could have an important influence on the population. Knowing that opinion and what factors influence it is important to improve the attitude towards organ donation and transplantation. Design: A multicenter, sociological, interdisciplinary and observational study including university nursing diploma students in a complete academic year. Methods: Selected and randomized sample was taken of students from 52 of the 111 faculties and nursing schools and faculties in Spain with teaching activity PARTICIPANTS: A sample of 10,566 students was selected stratified by geographical area and year. Measurement instrument: The instrument used was a validated questionnaire of attitude toward organ donation and transplantation, self-administered and completed anonymously. Results: Completion rate: 85 % (n = 9001). Of the students surveyed, 78 % (n = 7040) would donate their organs after dying. Variables related to a favourable attitude: (1) Interest in listening to a talk about organ donation and transplantation [Odds ratio 1.66, 95 % confidence interval 2.05-1.35]; (2) Family discussion [Odds ratio 2.30, 95 % confidence interval 2.79-1.90] or discussion with friends about organ donation and transplantation [Odds ratio 1.56, 95 % confidence interval 1.86-1.31]; (3) Knowing that one's father [Odds ratio 1.54, 95 % confidence interval 1.94-1.22], mother's [Odds ratio 1.44, 95 % confidence interval 1.82-1.13] or partner [Odds ratio 1.28, 95 % confidence interval 1.60-1.03] has a favourable opinion; (4) Having a good self-assessment of information about organ donation and transplantation [Odds ratio 2.94, 95 % confidence interval 4.90-1.78]; (5) Not being worried about possible mutilation of the body after donation [Odds ratio 2.73, 95 % confidence interval 3.36-1.72]. Conclusions: Nursing students in Spain tend to have a favourable attitude toward organ donation and transplantation although more than 20 % of those surveyed are not in favour. Tweetable abstract: To maintain a high rate of organ donation for organ transplantation, it is necessary to improve the social awareness of future generations of nurses towards organ donation.