Mollidgewock Brook flows out of Mollidgewock Pond in the town of Upton, Maine, and heads west, quickly entering New Hampshire. The brook flows west and north through swampy areas and past low hills in the township of Cambridge before joining the Androscoggin River in the town of Errol.
In 2009, The Trust for Public Land added 3,100 acres (1,300 ha) of the Mollidgewock Brook lands to the Umbagog National Wildlife Refuge. The remaining 1,800 acres (730 ha) were added to 13 Mile Woods, Errol's community forest.[2]Mollidgewock State Park is located along the Androscoggin River opposite the mouth of Mollidgewock Brook.