Lake Wentworth lies in the Lakes Region of east central New Hampshire, south of the White Mountains. More specifically, it lies in Carroll County, wholly within the boundaries of the township of Wolfeboro, ten miles west of the Maine border, forty-five miles by road northeast of Concord, and one hundred and five miles by road north of Boston. Its geographical coordinates are latitude 43°34’ to 43°37’ North and longitude 71°7’ to 71°12’ West.
The nearest town is Wolfeboro, a mile to the west, a suburb of which, Wolfeboro Falls, extends almost to the shore of the lake. Wolfeboro Center and North Wolfeboro to the north, and East Wolfeboro or Cotton Valley to the east, are other near centers of population within the township. Ossipee and Sanbornville lie six miles from the lake, the former to the northeast, the latter to the southeast. Good macadam roads connect these points with Wolfeboro and pass close to the northern shore of the lake. Passenger trains of the Boston & Maine Railroad come only as near as Sanbornville, but daily freight trains run from Sanbornville to Wolfeboro. Bus lines serve Wolfeboro and the north shore of the lake. Private planes can use an airport at Wolfeboro.
Lake Wentworth is one of the feeder ponds for Lake Winnipesaukee, largest of New Hampshire lakes. A single outlet to the west, Smith River, provides this drainage, its flow controlled by a dam on a smaller pond through which the outlet passes.