Andersson was a lifelong Social Democrat, and served as party secretary for twenty years, between 1962 and 1982. He was appointed social affairs minister in 1982, and foreign minister in 1985. He held the post until the Social Democrats lost power in 1991.
"Sten Andersson was one of the Social Democratic Party's strongest political figures of the past fifty years," said prime minister Göran Persson in a statement released on Saturday night.
"He had strong roots in and was thoroughly knowledgeable about the workers' movement. He was an engaged debater, full of gladness and humour, and a fantastic organizer and internationalist."
Andersson's period as foreign minister was notable for his encouragement of dialogue between Israel and the PLO in the 1980s. He was serving as foreign minister when prime minister Olof Palme was murdered.
Andersson was born in Stockholm and gained his high school certificate while working at the Post Office.
He was chairman of the Stockholm branch of the Social Democrats for many years, and was a member of parliament between 1966 and 1994.
He was chairman of the Olof Palme International Centre until 1999.