Keuka Lake empties into another Finger Lake, Seneca Lake, from a stream, called Keuka Lake Outlet, at the lake's northeastern end in Penn Yan, New York. The stream empties into Seneca Lake at the village of Dresden. At one time the outlet was developed into a canal, the Crooked Lake Canal, connecting the lakes. This canal was later replaced by a railroad branch line which is now a hiking and cycling trail.
The lake is about 20 miles (32 km) long and varies in width from a half mile to two miles (1–3 km). The length of the shoreline is about 60 miles (96 km). It has a surface area of 11,730 acres (47 km²), and a maximum and mean depth of 186 feet (57 m) and 101 feet (31 m) respectively. This body of water possesses large and healthy populations of lake trout, brown trout, rainbow trout, landlocked salmon, smallmouth bass, largemouth bass, and yellow perch. The productive fishery is supported by huge numbers of baitfish, most notably alewives (sawbellies), and is a very popular lake with area fishermen.
The village of Penn Yan, New York is at the northeastern tip of the lake, and Branchport is at the northwestern tip. Hammondsport lies at the south end of the lake. Hammondsport was the home of Glenn Curtiss, a pioneer of naval aviation, and is now the site of the Glenn H. Curtiss Museum.
While the shore of the lake is primarily residential, Keuka College is located in Keuka Park on the western shore of the east branch and Keuka Lake State Park is located on the eastern side of the northwest branch of the lake. YMCA Camp Cory is located on the eastern side of the northeast branch of the lake. Camp Good Days and Special Times is located on the western side of the northwest branch of the lake. An important component of the economy of this region is based on grape growing and wine production and vineyards cover some areas sloping down to the lake.