| Alder Brook | |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | New York |
| Mouth: | Middle Branch Grass River |
| Mouth Location: | Degrasse, New York |
| Mouth Coordinates: | 44.3892°N -75.0231°W |
| Mouth Elevation: | 900feet |
| Basin Size: | 5.06sqmi |
Alder Brook flows into the Middle Branch Grass River near Degrasse, New York.[1]