New Alexandria is a borough in Westmoreland County, Pennsylvania, United States. The population was 560 at the 2010 census.
New Alexandria is located at 40°23′50″N 79°25′25″W (40.397254, -79.423591), along U.S. Route 22 approximately midway between Pittsburgh and Johnstown.
According to the United States Census Bureau, the borough has a total area of 0.8 square miles (2.1 km2), all of it land.
At the 2000 census there were 595 people, 254 households, and 186 families living in the borough. The population density was 704.2 people per square mile (273.5/km²). There were 271 housing units at an average density of 320.7 per square mile (124.6/km²). The racial makeup of the borough was 99.50% White, 0.17% Asian, and 0.34% from two or more races. Of the 254 households 28.3% had children under the age of 18 living with them, 60.2% were married couples living together, 9.4% had a female householder with no husband present, and 26.4% were non-families. 24.0% of households were one person and 11.4% were one person aged 65 or older.