Duncansville Borough is a small community located in central Blair County, close to the nearby urban centers of the City of Altoona and Hollidaysburg Borough. Duncansville is surrounded by Allegheny Township and Blair Township. The borough was originally part of Allegheny Township, but was incorporated into a borough in 1891.
With just over 1,200 residents, Duncansville Borough encompasses only half a square mile of land. While the borough itself is mostly urban/suburban, much of the area surrounding Duncansville consists of farms and woodlands. The majority of Duncansville is located within the Blair Gap Run watershed; Blair Gap Run winds from west to east through the Borough. A small, eastern section of the borough lies within the Beaverdam Branch watershed.