In the face of mounting environmental problems, it is essential that accurate and timely scientific information is available to inform policy development and guide management. Scientists have specialised knowledge necessary for evidenced-based decision making, but despite extensive literature on the interface between science and policy, there is little guidance on achieving policy relevance while maintaining high standards of scientific integrity. Here, we provide a set of principles for environmental scientists to engage with policy makers and environmental water managers. We propose the adoption of a contemporary pluralistic approach using a diversity of modes of engagement between scientists, policy makers, and managers. We define a set of ‘roles’ for environmental scientists to engage effectively with policy and management, and discuss the advantages and pitfalls of each. We illustrate the breadth of modes of engagement at the science-policy-management interface using an example from Australia’s largest river system, the Murray-Darling Basin. We challenge the anachronistic, yet persistent concept that engaging with industry or government compromises the objectivity of involved scientists. We argue that there are multiple assurance processes in place to protect scientific integrity. Society needs scientists to be actively involved in finding solutions to the many urgent environmental issues we are facing, and if our principles are followed there are opportunities for healthy interaction between science, policy, and management.