Understanding the impacts of urban expansion on ecosystem services (ESs) is important for sustainable development on regional and global scales. However, due to the uncertainty of future socioeconomic development and the complexity of urban expansion, assessing the impacts of future urban expansion on ESs remains challenging. In this study, we simulated the urban expansion in the Beijing-Tianjin-Hebei (BTH) urban agglomeration in China from 2013 to 2040, and assessed its potential impacts on ESs based on the Shared Socioeconomic Pathways (SSPs) and the Land Use Scenario Dynamics-urban (LUSD-urban) model. We found that urban land in the BTH urban agglomeration is expected to increase from 7605.25 km² in 2013 to 9401.75–11,936.00 km² in 2040. With continuing urban expansion, food production (FP), carbon storage (CS), water retention (WR), and air purification (AP) will decrease by 1.34–3.16%, 0.68–1.60%, 0.80–1.89%, and 0.37–0.87%, respectively. The conversion of cropland to urban land will be the main cause of ES losses. During 2013–2040, the losses of ESs caused by this conversion will account for 83.66–97.11% of the total losses in the whole region. Furthermore, the ES losses can cause considerable negative impacts on human well-being. The loss of FP will be equivalent to the food requirement of 3.68–8.61% of the total population in 2040, and the loss of CS will be 2.55–6.01% of the total standard coal consumption in 2013. To ensure sustainable development in the region, we suggest that effective policies and regulations should be implemented to protect cropland with high ES values from urban expansion.