According to the United States Census Bureau, the township has a total area of , of which , or 0.08%, are water. The crest of Bald Eagle Mountain forms the township's northern border. Two streams, Big Run in the west and Bender Run in the east, rise in Bastress Township and flow north, cutting through Bald Eagle Mountain to reach the West Branch Susquehanna River. The southernmost part of the township drains south to the Nippenose Valley in Limestone Township, which is drained by Antes Creek, a north-flowing tributary of the West Branch. Bear Pen Hollow is a ravine in the southeast corner of Bastress Township which drains east to Mosquito Creek, which also flows north to the West Branch of the Susquehanna.
According to the United States Census Bureau the township has a total area of  of which  or 008% are water The crest of Bald Eagle Mountain forms the township's northern border Two streams Big Run in the west and Bender Run in the east rise in Bastress Township and flow north cutting through Bald Eagle Mountain to reach the West Branch Susquehanna River The southernmost part of the township drains south to the Nippenose Valley in Limestone Township which is drained by Antes Creek a north-flowing tributary of the West Branch Bear Pen Hollow is a ravine in the southeast corner of Bastress Township which drains east to Mosquito Creek which also flows north to the West Branch of the Susquehanna