Instrument constituencies take shape in connection with the development of instrumental designs for policy and governance. They consist of entangled practices of research, consulting, public administration, facilitation, advocacy etc., which form and become established in relation to a specific design. Instrument constituencies create actors like experts and specialized organizations who live for the instrument, but who also live off the instrument. They can become active pushers of their instruments. Studying the formation and composition of instrument constituencies sheds light on social dynamics of the ‘supply side’ of designing policy. Because the spatial coverage and lifespan of instrument constituencies is greater than individual policy processes, they give us a view of extended historical and transnational policy dynamics. Instrument constituencies account for a hitherto neglected dynamic and form of agency that explain the often-observed paradox that policy solutions sometimes precede policy problems. We give an outline of the concept as it has been developed so far and discuss implications for the field of policy design.