Rattling Run begins on a mountain in Butler Township.
It flows west-southwest for a few tenths of a mile before turning northwest and flowing through the Gordon Reservoir.
The stream then turns west-southwest for several tenths of a mile, entering a valley and flowing alongside Highridge Park Road/Gordon Mountain Road.
It then turns northwest for several tenths of a mile before turning north-northwest and entering Gordon.
Here, it leaves its valley and continues flowing north-northwest.
After a few tenths of a mile, it reaches its confluence with Little Mahanoy Creek.

Rattling Run joins Little Mahanoy Creek 0.32 miles (0.51 km) upstream of its mouth.
Rattling Run begins on a mountain in Butler Township. It flows west-southwest for a few tenths of a mile before turning northwest and flowing through the Gordon Reservoir. The stream then turns west-southwest for several tenths of a mile, entering a valley and flowing alongside Highridge Park Road/Gordon Mountain Road. It then turns northwest for several tenths of a mile before turning north-northwest and entering Gordon. Here, it leaves its valley and continues flowing north-northwest. After a few tenths of a mile, it reaches its confluence with Little Mahanoy Creek.
Rattling Run joins Little Mahanoy Creek 0.32 miles (0.51 km) upstream of its mouth.
Rattling Run (Little Mahanoy Creek tributary)