The route is a two-lane undivided road that runs through rural areas and suburban development to the north of York.

The route fully enters Dover Township as it turns northeast into wooded areas of homes before passing a mix of farmland and residences.

Upon crossing Bull Road, PA 921 heads into Conewago Township and passes more agricultural areas with some patches of woods and housing.

The road intersects PA 297 in the community of Zions View, where it makes a turn to the east and crosses the Little Conewago Creek, becoming the border between East Manchester Township to the north and Manchester Township to the south as it passes under Interstate 83.

Immediately after, PA 921 turns northeast into East Manchester Township and passes farm fields.