PA 899 begins at an intersection with PA 36 in Barnett Township, Jefferson County, heading north on a two-lane undivided road. The route passes between woods to the west and fields to the east before heading through forested areas, turning to the northeast.[2][3] The road crosses the Clarion River into Barnett Township in Forest County and turns northwest at Clarington, running along the northeast bank of the river. PA 899 turns north away from the river and continues through more forests. The road winds northwest through more wooded areas with occasional fields, passing through . The route crosses into Jenks Township and continues north through more forests with some fields and homes. PA 899 turns northeast and crosses an abandoned railroad line, passing through before turning north and ending at PA 66.[2][4]