Advocacy in evaluation involves a set of inherent tensions in the commissioning and practice of policy and program evaluation. The two primary tensions are (1) advocacy for particular social goods, or what are the most legitimate values that can be advanced in evaluation studies and (2) advocacy for particular constituencies, or who comprises the most important audiences for evaluation studies. These tensions arise because evaluation is both a technical and a social practice that typically takes place in politicized contexts and because evaluations of programs, especially public programs, have multiple legitimate interested audiences. This entry concentrates on evaluations of public programs and policies wherein the issues of advocacy are most salient and consequential.