Alnus viridis is a shrub species encroaching mountain pastures in Central Europe, with negative ecological and economic consequences. Although targeted grazing with robust livestock breeds can limit shrub expansion, its effectiveness in restoring plant diversity and forage quality remains poorly documented. We evaluated the impact of Highland cattle grazing on vegetation dynamics in a summer pasture in the Swiss Alps, in the canton of Vaud. Since 2019, a herd has grazed two 7–8 ha paddocks at an average stocking rate of 0.22 LU ha⁻¹ year⁻¹, and a third paddock was included in 2020. We characterized long-term vegetation cover changes of the paddocks through manual classification of orthophotos and satellite images from multiple years. Moreover, we assessed the impact of five years of Highland cattle grazing on vegetation structure by surveying A. viridis shrubs and recording branch mortality, resprouting, and understory light availability in relation to cattle stocking density measured through GPS livestock tracking. Finally, we conducted botanical surveys along permanent transects in 2019 and 2024 to evaluate changes in plant species richness and pastoral value over time. After the introduction of Highland cattle, shrubland cover decreased by 4%. Higher livestock stocking density around shrubs increased branch mortality and understory light availability. The number of resprouts also increased with stocking density. Species richness increased from 25.5 to 32.2, and the pastoral value of open pastures improved from 12.9 to 17.7. Overall, our findings show that Highland cattle effectively reduce A. viridis cover, increase understory light availability, thereby promoting plant diversity and pastoral value of grasslands. However, the resprouting response to higher livestock density indicates that a five-year grazing period is insufficient to fully control woody encroachment. Therefore, long-term grazing management is essential to restore pastures encroached by A. viridis.