Junior Senior formed in 1998 when Jesper Mortensen and Jeppe Laursen got back together after their previous band Ludo-X broke up in 1995. The band signed a deal with Danish label Crunchy Frog Records.
Mortensen and Laursen announced on their blog that they would split and pursue solo projects on September 26, 2008. Both Junior and Senior have launched new projects. In 2008, Mortensen released a 12" single called "Trust Tissue" under the moniker I Scream Ice Cream on Kitsune Records. In 2010, Mortensen formed the group MAKE OUT. Laursen is reportedly working on a debut album.