Background: Nurses are in a privileged position to detect environmental risks among children.The objective was to determine attitudes, knowledge, and skills related to children's environmental health in undergraduate nursing students. Method: A cross-sectional study was designed in eight universities (n = 2,462) from September 2017 to June 2018. Descriptive values and multivariate analysis of variance were calculated using three questionnaires. Results: Of the total 2,462 students in the sample, 2,155 had a good attitude regarding addressing children's environmental health problems, 501 had good knowledge, and 1,162 had good skills. Students who had attended a session on sustainability more than 3 months prior had a better attitude (9.93%), knowledge (11.16%), and skills (3.82%). Second course students and men had better environmental competency (p < .001). Conclusion: Undergraduate nursing students have good attitudes; however, they lack knowledge and skills. There is a need to include children's environmental health in nursing curricula.