In West Ossipee, NH 25 (now known as Ossipee Mountain Highway) passes near the historic Whittier Bridge before crossing over the Bearcamp River and coming to a T-intersection with NH 16 and joining it southbound along White Mountain Highway. Heading southeast past the western shore of Ossipee Lake, there are two intersections with NH 16B before NH 25 leaves White Mountain Highway to the northeast at an interchange in Center Ossipee. Passing through the Ossipee Lake Natural Area south of Ossipee Lake, NH 25 crosses into Effingham, passing through the village of Effingham Falls along a brief concurrency with NH 153, then crossing the Ossipee River into the town of Freedom, New Hampshire. Now following the northern bank of the Ossipee River, NH 25 reaches its eastern terminus at the Maine border, with the roadway continuing into the town of Porter, Maine, as Maine Route 25.