Jan O. Karlsson studied economics, political science and history at Stockholm University, before becoming an undersecretary at the Ministry of Agriculture in 1962.

Following the election in 1988 he was instead made chairman for the government commission of inquiry on metropolitan areas, and in 1990 once again advisor and coordinator at the prime minister's Office.

[1] Jan O. Karlsson's tenure as minister was far from smooth, his relation with the local press was troublesome, often attributed to his late father, who also was a high ranking social democratic politician, who died of a heart attack during an interview with a journalist.

In spite of a number of minor political scandals – he, among other things, referred to George W. Bush as "that damn Texan geezer" ("den där jävla texasgubben")[2] and abruptly murmured (with a microphone attached to his jacket) "now we better see an end to these fag issues" (nu får det väl vara slut på de här bögfrågorna) during a SIDA conference[3] – he was able to maintain the trust of prime minister Göran Persson and keep his place in the Cabinet.

His appointment as acting Minister for Foreign Affairs following the death of Anna Lindh on 11 September 2003, was a short-term solution.