Grassland ecosystems support well-being with food, shelter, income, and culture of herdsmen. While the association between ecosystem services and human well-being has been widely studied, such association is understudied in grassland ecosystems. This study aims to fill this gap through a case study of Xilinhot City, Inner Mongolia Autonomous Region, China. We examined the association between grassland provisioning services and herdsmen's well-being between 1985 and 2015 through participatory observations, interviews, surveys, and Bayesian belief network modeling. Considering the uncertainties of weather and sheep prices, we developed four scenarios to examine the future well-being of herdsmen. Our results show that the most important factor for herdsmen's well-being was income, which is highly sensitive to the market price of sheep and precipitation. Considering the uncertainties of sheep prices and precipitation, scenario analysis revealed a divergence between income and well-being. While herdsmen's income is most likely to increase with low precipitation and increased sheep prices, their well-being is most likely to improve with abundant precipitation and increased sheep prices. Based on our findings, we argue that developing alternative income sources (e.g., tourism), reducing dependence on government subsidies through commercial insurance, and branding lamb with grassland ecosystem to alleviate the impact of price fluctuations would help improve herdsmen's well-being in all scenarios.