Johansson worked as a Journalist and editorial Writer for the social democratic daily newspaper Arbetet Nyheterna 1994-1997 and as political expert in the Prime Minister's Office from 1997 to 1998.
Johansson was previously Minister for Public Health and Social Services in the Persson Cabinet from 2002 to 2006 and has been a Member of the Riksdag for the southern Skåne County electoral district since the 1998 elections. As a member of the opposition he was Chairman of the Committee on Justice of the Riksdag from 2010 to 2014.
In 2010 author Christer Isaksson described Johansson as a member of the left-leaning faction of the Social Democratic Party. He is also a member of the Swedish Humanist Association and has previously served on the association board.
On Monday afternoon, March 23, 2015, Johansson was attacked at the Broby hospital asylum center in Broby, Östra Göinge Municipality, Skåne. A 25-year-old man charged at Johansson and sprayed him with a fire extinguisher. The attacker was quickly apprehended and Johansson was not injured in what was referred to as a premeditated assault.
