Following the 2009 federal elections, Oettinger was part of the CDU/CSU team in the negotiations with the FDP on a coalition agreement; he joined the working group on economic affairs and energy policy, led by Karl-Theodor zu Guttenberg and Rainer Brüderle.

In a leaked diplomatic cable from the United States Embassy entitled "Lame Duck German Governor Kicked Upstairs as New Energy Commissioner in Brussels," U.S. Deputy Chief of Mission in Germany, Greg Delawie notes: "Chancellor Angela Merkel nominated Baden-Wuerttemberg (BW) Minister President Guenther Oettinger as EU Energy Commissioner primarily to remove an unloved lame duck from an important CDU bastion".

Delawie's cable further states: "Oettinger is noted for a lackluster public speaking-style, and some commentators have asserted that Merkel, who has often stood out at EU meetings, wanted to appoint a German Commissioner who would not outshine her!"

In the Second Barroso Commission, Oettinger was allocated the Energy portfolio, which had just grown in importance after the Lisbon Treaty gave the EU complete authority in the area.

[4] At his confirmation hearing before the European Parliament in 2010, Oettinger pledged to enforce the principle of solidarity on energy policy as enshrined in the EU's Lisbon Treaty so that no member state could be left disadvantaged.

He struck a chord with parliamentarians by basing his security of supply strategy equally on diversifying gas transportation routes from third countries and promoting indigenous renewable energy.

[4] The first phase of Oettinger's term was dominated by the Nabucco pipeline debate, his many trips to Azerbaijan and the Caspian region as well as his negotiations with Russian energy company Gazprom.

[6] In an interview with Die Welt in 2014, he criticized the German Federal Government's plan to allow longer-serving employees to retire at the age of 63 for the message this sent to cash-strapped peripheral eurozone states like Greece, Spain and Portugal.

[17] Economic policy In an op-ed published in both the Financial Times and Les Échos in November 2014, Oettinger questioned whether President François Hollande had the "willingness to act" to reform the French economy[18] and said the Commission should insist France undertake "concrete and quantifiable measures coupled with precise deadlines" as a condition for a fresh deficit extension;[19] in response, members of the French Socialists called for Oettinger to resign.

[20] On 1 January 2017 Oettinger was reassigned to the Budget and Human Resources portfolio, following the resignation of Kristalina Georgieva with effect from 31 December 2016 to take up a new position as chief executive officer of the World Bank.

[2] On 11 April 2007, Oettinger gave a controversial eulogy on one of his predecessors as Minister President of Baden-Württemberg, Hans Filbinger who had been forced to resign in 1978 after allegations surfaced about his role as a navy lawyer and judge during World War II.

As a result, several MEPs wrote a letter of protest to EU Commission President José Manuel Barroso, demanding his apology or resignation.

Oettinger subsequently received criticism both from European sources and a Chinese government spokesman, and several days later issued a statement apologizing for "any remark that was not as respectful as it should have been".

[49] Three days later, Oettinger's wife was reported to have already been in a relationship for nine months with Otmar Westerfellhaus, Managing Director of the Porsche car-manufacturing subsidiary in Mannheim.

[50] In 2008, after separating from his wife, Oettinger's liaison with Friederike Beyer, a PR events organiser from Hamburg, who is 25 years his junior, enjoyed wide coverage in the German press.