The headwaters of Leggetts Creek are outside of the Lackawanna Valley. At Providence, the creek flowed directly southeast prior to the glacial period, reaching the Lackawanna River approximately downstream of its current location. However, the course now flows to the east instead. The old course of the creek has been built over. There is a ledge on the north bank of Leggetts Creek in its lower reaches. The creek makes a sharp eastward bend around Providence. From this point downstream to its mouth, it flows through a rocky channel that contains a thick covering of till on its upper walls. A run of the river dam known as the High Service Dam is on Leggetts Creek in Scranton. The dam is wide. A rock formation known as the Campbell's Ledge Black Shale occurs in the vicinity of Leggetts Creek. This rock formation contains shale and coal. The ledge on the northern bank of the creek was in the early 1900s noted to contain a large mass (up to a million tons) of sandy till. In early March 2013, the temperature in the vicinity of Leggetts Creek was once measured to be . A 2013/2014 study found the water temperature of the creek to range from , with an average of . The watershed of Leggetts Creek has an area of . Upstream of the tributary Leach Creek, the watershed has an area of . It is one of the larger tributaries of the Lackawanna River. The mouth of the creek is in the United States Geological Survey quadrangle of Scranton. However, its source is in the quadrangle of Dalton. The creek is a third-order stream and is the third-largest tributary of the Lackawanna River, not counting the East Branch Lackawanna River and the West Branch Lackawanna River. Municipalities that the watershed is in include Scott Township, South Abington Township, Abington Township, Clarks Green, Clarks Summit, Newton Township, Dickson City, and Scranton. Major land uses in the watershed of Leggetts Creek include high-density residential, neighborhood commercial, and open space. Lakes in the watershed of Leggetts Creek include the Griffin Reservoir, Maple Lake, and Summit Lake. These bodies of water are in South Abington Township and Scott Township. The Griffin Reservoir supplies water to people in the Leggetts Creek watershed. The creek and the reservoir serve as a supplemental drinking water supply for more than 100,000 people as of the late 20th century.