Reputational threats are key to understanding public services’ behaviour. Previous research has viewed external performance assessments as an unwelcome imposition on public managers and a threat to organizational identity. Analysing the adoption of a self-imposed process of peer-led assessment by public managers in UK local government we show how the absence of performance assessment was seen as a reputational threat. Engaging proactively with the new voluntary assessments becomes an essential tool for active reputation management. We find that reputation does not only shape the responses to external performance assessment but the external performance assessment itself.