This study contributes to the evolving needs of decision support for evidence-informed health policymaking. Its aim was to bring more formal consideration of context and a broader conception of evidence into public health policymaking, giving due prominence to all relevant types of evidence. A sequential mixed methods approach was used to undertake the development of a decision aid to support evidence-informed public health policy. A meta-narrative review and focus group were conducted to inform the initial development of the proposed aid. Key informant interviews followed, providing preliminary feedback for refinement of the tool. The final deliverable was a beta-version of a decision aid designed to assist policymakers with making evidence-informed public health policy decisions, ready for pilot testing and further development.