Formed in Tokyo, Japan in 2002. The bands idea at first was to have a dark and morbid sound. None of the band members at first knew how to play any instruments as in all past bands they did vocals. Their first recording, in the form of a free demo tape that was limited to 30 copies, was distributed at their first gig at Koiwa Death Fest Vol.2, around March 2003, in Japan. In July of the same year, the self-titled demo album was released. By April of the following year, they had released another demo album, entitled Endless Nauseous Days, and were working towards their debut full-length CD.
January 2006, Gallhammer was signed to Peaceville Records, on the recommendation of Darkthrone. A CD/DVD pack, entitled The Dawn of..., was released, containing a CD, demo & rehearsal footage, and a DVD recording of Gallhammer performing in Okayama and 5 concerts in Tokyo.
Gallhammer released their second full-length album, Ill Innocence, through Peaceville Records on September 24, 2007, followed by a European tour. As of March 2008, they did a second European tour. They also played at the Inferno Metal Festival in June.
They are also known for being one of few all female extreme metal band.