As innovation policy instruments are never applied in isolation, this chapter reviews the evidence on policy mixes and the interplay of instruments in innovation policy. The chapter starts with a multi-dimensional conceptualisation of mixes and interplay, in particular distinguishing between designed versus emergent mixes. Overall, the evidence and evaluation practice as to policy mix and interplay are scarce, reflecting not only the challenges of analysing the interplay of instruments, but also the general neglect in policy making to take interplay into consideration. The chapter first presents and analyses evidence from the few evaluations which have explicitly examined how instruments interact, focusing on interplay between direct and indirect measures as well as supply and demand measures. In general, the additive effect of multiple measures targeting the same actor groups is limited. Secondly, the chapter looks at evidence from reviews of policy mixes at the country or system level. Those country reviews have mainly been conducted under the auspices of the OECD or the EU. They highlight the trends of applying policy mixes and comment on their appropriateness, identify common policy gaps and coordination issues, but rarely deliver hard evidence of system-wide interplay. Thirdly, the review looks at instances where policies or instruments have been deliberately used together, as designed mixes across policy institutions or as the portfolios of specific agencies. The chapter finally draws lessons as to policy mix practice using the conceptual framework developed.