Ajattara formed in 1996 as a side project of Amorphis singer Pasi Koskinen. Their first release was a demo tape entitled Helvetissä on syntisen taivas which was released in 1998. The band then signed to Spikefarm Records and went on to release three albums - Itse in 2001, Kuolema in 2003 and Tyhjyys in 2004. These albums were met with largely good reviews.Ajattara then went onto release a Christmas Single in the Novembers of 2004 and 2005, which is a tradition they have done for the last three years. They were entitled Ilon juhla (2004) and Joulu (2005). The band then went onto release another album in 2006, entitled Äpäre, which was met with similar reviews as their last three albums. The band continued with the Christmas single tradition of 2004 and 2005 by releasing a single entitled Sika in 2006.
Towards the end of 2006 Ajattara's original line-up ceased to exist, when Pasi Koskinen made Nazi salutes and other related political statements during a concert.Ajattara then reformed with a new line up some time during 2007. The band entered the studio on June 1, 2007 to begin recording on the album Kalmanto which was released on September 5, 2007. However, this album was not met with such good reviews as Ajattara's other albums, as some critics said the album sounded chaotic and forced. In April 2009 Ajattara released their 6th album entitled Noitumaa, this time being an all-acoustic album, which received clearly better reviews than the previous release.
The band made an announcement on its Facebook page on 15 April 2012 that it had split up, reasons are unknown.
Ajattara combine elements of black metal that play a style of black metal not dissimilar to Celtic Frost and to a lesser extent Samael. The combined use of synthesisers and heavy guitar sounds give Ajattara a distinct "grimey" sound. The lyrical themes of Ajattara usually deal with death, evil and paganism.