The formation was a result of a successful petition and election by the citizens of the northeastern corner of Lycoming County who were under the leadership of H. I. McNett, for whom the township was named.

McNett Township occupies the northeastern corner of Lycoming County.

The township's northwestern boundary, with Tioga County, follows Lycoming Creek, a southwestward-flowing tributary of the West Branch Susquehanna River.

No state highways pass through the township, although Pennsylvania Route 14 runs up the Lycoming Creek valley on the Tioga County side of the stream.

Williamsport, the Lycoming county seat, is 33 miles (53 km) to the southwest via PA-14 and U.S. Route 15.

About 24.5% of families and 29.9% of the population were below the poverty line, including 37.0% of those under the age of eighteen and 17.0% of those sixty five or over.