Mifflin is a borough in Juniata County, Pennsylvania, United States.

At one time, Mifflin, as well as the small community of Denholm lying directly north of the town, was an important stop along the Pennsylvania Railroad.

The railroad tracks still pass through the town, but they are now owned by the Norfolk Southern Railway.

The Pennsylvania Railroad depot still stands in Mifflin, although it has long been abandoned.

[5] According to the United States Census Bureau, the borough has a total area of 0.2 square miles (0.52 km2), all land.