Species rich grasslands provide ecosystem services such as floral and faunal diversity, livestock forage, carbon sequestration and water regulation. However, the best combinations of sward diversity and management intensity to achieve the above-mentioned ecosystem services are not fully known. To address this, we established experimental grasslands with three sward types with varying diversity levels: productive monoculture (PM; perennial ryegrass (Lolium perenne)), biodiverse (BD) and productive biodiverse (PBD; i.e., diverse sward with species selected to increase forage quantity and quality) and with a management gradient ranging from extensive (i.e., low input, late mowing) to intensive (i.e., high input, early mowing). After three years, we found successful establishment of biodiverse swards with high forb cover, particularly under extensive management, but changes to meadow bird habitat parameters (i.e., sward height and vertical vegetation density) were negative. Forage dry matter yield was highest in BD and intensively managed swards in 2019 and 2020, but intensively managed swards had higher dry matter yield regardless of sward type in 2020. Forage N concentration was highest in PBD swards and digestible organic matter was highest in PM and PBD swards, indicating the productive plants species added to the PBD swards improved forage quality. Improvements in carbon sequestration and water regulation were minimal. Collectively, diverse swards, different management regimes and their interactions benefit certain ecosystem services, but not all. Taken together, these findings pull focus on the need for careful consideration of sward species composition, management and their interactions in order to maximise specific ecosystem services in young, mown grasslands