Assessing trade-offs between forage production and ecological characteristics delivered by grasslands is a growing concern for stakeholders and scientists. We sampled 50 grasslands from the Vosges Mountains (north-eastern France), and measured the agronomic (forage yield and quality) and biodiversity characteristics of each grassland. We assessed yield through dry matter production; fodder quality through organic matter digestibility, protein, energy and mineral content; and biodiversity through total and oligotrophic plant species richness and ecological indices. Using a Hierarchical Clustering on Principal Components, our results show that grasslands can be classified into three classes. The first class is made of grasslands associated with high quality forage but poor ecological value, the second of diverse and productive grasslands associated with poor forage quality, and the last one of grasslands and moors of high ecological value but poor forage yield and quality. These classes are mainly determined by agricultural practices and soil properties. Our study highlights the trade-offs between the agronomic and ecological characteristics of grasslands: grasslands cannot produce high yields, qualitative forage and protect biodiversity at the same time. We argue that agronomists and naturalists must work together at both farm- and landscape-scales to produce forage in sufficient quantity and quality while protecting biodiversity.