Background: Public health emergencies require rapid responses from experts. Differing viewpoints are common in science, however, “mixed messaging” of varied perspectives can undermine credibility of experts; reduce trust in guidance; and act as a barrier to changing public health behaviours. Collation of a unified voice for effective knowledge creation and translation can be challenging. This work aimed to create a method for rapid psychologically-informed expert guidance during the COVID-19 response. Method: TRICE (Template for Rapid Iterative Consensus of Experts) brings structure, peer-review and consensus to the rapid generation of expert advice. It was developed and trialled with 15 core members of the British Psychological Society COVID-19 Behavioural Science and Disease Prevention Taskforce. Results: Using TRICE; we have produced 18 peer-reviewed COVID-19 guidance documents; based on rapid systematic reviews; co-created by experts in behavioural science and public health; taking 4–156 days to produce; with approximately 18 experts and a median of 7 drafts per output. We provide worked-examples and key considerations; including a shared ethos and theoretical/methodological framework; in this case; the Behaviour Change Wheel and COM-B. Conclusion: TRICE extends existing consensus methodologies and has supported public health collaboration; co-creation of guidance and translation of behavioural science to practice through explicit processes in generating expert advice for public health emergencies.