The north side of Sandwich Mountain drains into Drakes Brook, thence into the Mad River, Pemigewasset River, Merrimack River, and thence into the Gulf of Maine at Newburyport, Massachusetts. The west side of Sandwich Mountain drains into Smarts Brook, thence into the Mad River. The southwest flank of Sandwich Mountain drains into the Beebe River, thence into the Pemigewasset River. The south side of Sandwich Mountain drains into the Cold River, Bearcamp River, Ossipee River, and the Saco River, which reaches the Gulf of Maine at Saco, Maine. The east side of Sandwich Mountain drains into Pond Brook, thence into the Cold River.