The division was formed at the end of December 1914 and organized over the next month, arriving in the line in early February 1915.
The division was recruited in various Prussian provinces: Brandenburg, Pomerania, and West Prussia.
The 81st Reserve Division initially fought on the Western Front, seeing its first action in the trenches west of the Somme.
It continued fighting across the border between Austro-Hungarian Galicia and Russian Poland, fighting in a series of battles leading to the taking of Brest-Litovsk in August and Pinsk in September, and then settled into positional warfare in the Pripyat Marshes.
Over the course of the war, other changes took place, including the formation of artillery and signals commands and the enlargement of combat engineer support to a full pioneer battalion.