The importance of ecosystem services (ESs) has been widely recognized and studied since 2000. However, research on the interactions (synergies and trade-offs) among ESs and hotspots of ESs is limited. This study focused on the Asian Water Tower (AWT) region (17 countries) and assessed the importance of five critical ESs by four quantitative models, analyzed the interactions among ESs, and identified hotspots of ESs using hotspot analysis. The results showed that the areas with “high importance” of the composite ESs accounted for 6.3% of the AWT region, and they were distributed mainly in mountain and coastal areas. Additionally, high synergies among the five ESs were observed in areas with “high importance” of the composite ESs, whereas poor synergies among ESs were found in areas with “relatively high importance” of the composite ESs. Furthermore, a total of 132 hotspot basins (28.4% of the AWT region) of the composite ESs were identified, and 23.2% of the hotspot basins were areas with “highly and relatively highly synergistic” ESs. The results provide evidence-based support for setting ecosystem protection goals, achieving win-win ESs, and improving ecosystem management efficiency. Overall, this study can deepen the understanding of the interactions and hotspots of ESs in the AWT region.