From 1985 to 1988 Faymann was a consultant at the Zentralsparkasse Bank (now Bank Austria), which he left to become director and provincial chairman of the Viennese Tenants' counselling. He was also provincial chairman of Socialist Youth Vienna (Sozialistische Jugend Wien) from 1985 until 1994, when he became a member of the Viennese state parliament and municipal council; where he held various positions concerning housing construction and urban renewal.
Faymann was Federal Minister for Transport, Innovation and Technology in the Cabinet of Chancellor Alfred Gusenbauer. On 16 June 2008 Faymann succeeded Gusenbauer as chairman of the Social Democratic Party of Austria (SPÖ) and led the party in the snap legislative elections, held on 28 September 2008. The election was famously preceded by Faymann and Gusenbauer together announcing a shift in the party's position towards the signing of new EU treaties, which they did by writing an open letter to Hans Dichand, the editor of the yellow press medium Kronen Zeitung, the largest newspaper in the country. This caused a scandal within the party, because the shift was not decided by any party committee, and led the pro-EU Austrian People's Party (ÖVP) to end the existing coalition, thus causing the elections. Faymann was known for his good relationship with the now-deceased Dichand, who would also support him in the following election campaign. Although the SPÖ lost 11 seats, and had a 6% swing against it (in fact, their worst result since World War II), they came ahead of their main rivals Austrian People's Party with regard to seats (57 to 51) as well as to share of the vote (29.26% to 25.98%). Afterwards, Faymann renewed the coalition with the Austrian People's Party, as he had announced before the election.