This chapter helps make sense of ex-post policy evaluation as a governing practice. Judging the success or failure of public policy, its outcomes and effects have become a fundamental part of governing. While it is acknowledged as a normative practice, the normative power of evaluation as a constitutive practice remains underexplored. This chapter makes a modest contribution towards understanding evaluation as a constitutive practice. First, exploring how policy evaluation emerged as a practice and came to be a more formalised part of policy work, followed by a discussion about the normative power of policy evaluation and the ways it can reorient policy for progressive social change.