Human biomonitoring involves the use of human samples and data to investigate exposure to environmental chemicals and their impact on human health. HBM4EU developed a coordinated and harmonized approach involving 29 countries in Europe plus Israel. Addressing ethical issues has been an indispensable prerequisite, from the application phase, grant agreement, project performance to the closing of the project. HBM4EU has established a better understanding of the ethics in such projects and the need for a standardised way of reporting and handling of ethics and data exchange, securing compliance with ethics standards, transparency, transferability and sustainability. The main reflections were: Knowledge: Ethics awareness, norms and practices are dynamic and increased throughout the project, much learning and experience is achieved by practice and dialogue. Attitude: Rules and standards were very diversely known and needed to adhere to local practices. Assistance: Good results achieved from webinars, training, help desk, and individual consultations. Standardisation: Was achieved by templates and naming convention across documents. Management: The establishment of the SharePoint directory with uploading of all requested documents assisted collaboration and exchange. Also, a designated task for ethics within the management/coordination work package and the enthusiasm of the task leader were essential. Compliance: Some, but not all partners were very good at complying with deadlines and standards. Transferability and sustainability: All documents are archived in the SharePoint directory while a system assuring updating is recommended. Transparency: Assured by public access to annual ethics reports. The ethics reports bridged to the annual work plans (AWPs). Evaluation: The Ethics Check by the Commission was successful.