There is strong, and growing, evidence documenting health inequities across the world. However, most governments do not prioritize policies to encourage action on the social determinants of health and health equity. Furthermore, despite evidence concerning the benefits of joined-up, intersectoral policy to promote health and health equity, it is rare for such policy approaches to be applied systematically. To examine the usefulness of political and social science theory in understanding the reasons for this disjuncture between evidence and practice, researchers and public servants gathered in Adelaide for an Academy of the Social Sciences in Australia (ASSA) Workshop. This paper draws together the learnings that emerged from the Workshop, including key messages about the usefulness of various theories as well as insights drawn from policy practice. Discussions during the Workshop highlighted that applying multiple theories is particularly helpful in directing attention to, and understanding, the influence of all stages of the policy process; from the construction and framing of policy problems, to the implementation of policy and evaluation of outcomes, including those outcomes that may be unintended. In addition, the Workshop emphasized the value of collaborations among public health researchers, political and social scientists and public servants to open up critical discussion about the intersections between theory, research evidence and practice. Such critique is vital to render visible the processes through which particular sources of knowledge may be privileged over others and to examine how political and bureaucratic environments shape policy proposals and implementation action.