The population was 479 at the 2010 census.
The township is located in north-central Carbon County and is bordered to the north partially by Luzerne County. The Lehigh River forms the winding eastern border of the township, carving a gorge up to 1,000 feet (300 m) deep. The township's villages include Leslie Run and Rockport. The borough of Weatherly is on the western side of the township but is a separate municipality.
According to the United States Census Bureau, Lehigh Township has a total area of 26.4 square miles (68.5 km2), of which 26.1 square miles (67.7 km2) is land and 0.3 square miles (0.8 km2), or 1.12%, is water.
As of the census of 2000, there were 527 people, 193 households, and 156 families residing in the township. The population density was 20.1 people per square mile (7.8/km²). There were 237 housing units at an average density of 9.0/sq mi (3.5/km²). The racial makeup of the township was 97.91% White, 1.71% Native American, 0.19% Asian, and 0.19% from two or more races. Hispanic or Latino of any race were 0.76% of the population.
There were 193 households, out of which 31.6% had children under the age of 18 living with them, 66.8% were married couples living together, 8.8% had a female householder with no husband present, and 18.7% were non-families. 16.6% of all households were made up of individuals, and 7.8% had someone living alone who was 65 years of age or older. The average household size was 2.66 and the average family size was 2.92.
In the township the population was spread out, with 24.1% under the age of 18, 6.1% from 18 to 24, 26.6% from 25 to 44, 27.3% from 45 to 64, and 15.9% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 90.3 males. For every 100 females age 18 and over, there were 95.1 males.
The median income for a household in the township was $40,000, and the median income for a family was $43,333. Males had a median income of $32,083 versus $26,042 for females. The per capita income for the township was $17,883. About 8.0% of families and 10.8% of the population were below the poverty line, including 19.8% of those under age 18 and 9.3% of those age 65 or over.