Ecosystem services (ES) is an important approach to biodiversity protection in political rhetoric and policy practice, but it is also highly contested. This paper analyzes the introduction of ES in Swedish environmental policy and how it is contested by key stakeholders, and discusses its implications for biodiversity governance. The results show that although ES is widely accepted on an abstract and conceptual level, critical features and functions are highly contested. These primarily concern the valuation of nature, and the appropriateness of different policy instruments and institutional structures. The paper concludes that while the controversy surrounding ES fills an important role by reinvigorating debate and stimulating reflections on biodiversity loss, it also illustrates how ES is used to further particular values and beliefs and to challenge traditional biodiversity-protecting strategies. Understanding these policy controversies is central to addressing the challenges of transforming the promises of ES into practical policies.