Aims and objectives To identify final-year undergraduate students and new graduate nurses' behavioural intentions towards medication safety across four countries. Background Medication errors are a common and avoidable occurrence, being costly for not only patients but also for health systems and society. Design A multi-site cross-sectional study. Methods A self-administered survey was distributed to students and new graduate nurses in South Africa, India, Turkey and Australia. Descriptive statistics were calculated for all survey items. Multiple linear regressions were performed to predict behavioural intentions using the three Theory of Planned Behaviour constructs: attitudes, behavioural control and subjective norms. This study adheres to the STROBE guidelines. Results Data were analysed for 432 students and 576 new graduate nurses. Across all countries, new graduate nurses reported significantly higher scores on all the TPB variables compared with student nurses. Attitudes towards medication management were found significantly and positively related to intention to practice safe medication management for both student and new graduate nurses. Total perceived behavioural control was significantly and negatively related to intention to practice safe medication management for students. Conclusion Student and new graduate nurses showed favourable attitude, subjective norm, perceived behaviour control and intention in practising medication safety. However, differences in countries require further exploration on the factors influencing attitudes towards medication safety among student nurses and new nurse graduates. Relevance to clinical practice Understanding student and new graduate nurses' medication administration practices is important to inform strategies aimed at improving patient safety. The findings of this study highlight the need for an internationally coordinated approach to ensure safe medication administration by student and new graduate nurses.