In August 2007, Kleinfeld was appointed COO of Alcoa Inc. Beginning October 1, 2007, he oversaw the operative business for the US Aluminum concern. In May 2008, Kleinfeld was appointed as CEO of Alcoa, thus succeeding Alain Belda.
Kleinfeld was CEO of Siemens AG from 2005 until July 2007.On April 25, 2007, Siemens AG distributed a press release announcing that Kleinfeld was not available for a renewal of his contract. This was preceded by the supervisory board's indecisiveness in light of the ongoing corruption investigations at Siemens.
Kleinfeld has taken initiatives to reduce costs at Alcoa, including cutting back production and slashing jobs. The first company in the Dow Jones Industrial Average to announce results for the three months through June 2009, Alcoa reported narrower losses than forecasted on Wall Street. "Our cash generation initiatives, productivity improvements, and portfolio changes are working," said Mr. Kleinfeld in a written statement. "Now Alcoa has the staying power and reduced cost base to withstand the most serious downturn in the history of the aluminum industry." 
While CEO of Alcoa in 2009, Klaus Kleinfeld earned a total compensation of $11,214,266; which included a base salary of $1,400,000; a cash bonus of $3,754,800; options granted of $5,832,000; and other compensation of $227,466. 
Kleinfeld has worked for Siemens AG since 1987. His first position was in the company’s Corporate Sales and Marketing unit.
In January 2001, Kleinfeld moved to the United States, where he served first as chief operating officer (COO) and then – from 2002 to 2004 – as president and chief executive officer (CEO) of Siemens USA.
In January 2004, Klaus Kleinfeld was appointed to Siemens’ Corporate Executive Committee. Kleinfeld was appointed Vice President of Siemens AG in the middle of 2004 and Chief Executive Officer (CEO) on January 27, 2005, succeeding Heinrich von Pierer. As CEO, Kleinfeld set about restructuring Siemens. This led to the company turning in profits last year of $3.96 billion (up 35%) and increasing Siemens share price by 40%.  His attempts at modernization, however, brought him into conflict with the defenders of Siemens business culture, both inside and outside the company.  While generally viewed positively by the worldwide financial press, Kleinfeld regularly received criticism from the media in Germany, mostly for lack of social responsility against Siemens workers.
Under his leadership, the company's financially stricken mobile handset business was sold for a negative charge to Taiwan's BenQ in June 2005. The German subsidiary, BenQ Mobile GmbH & Co. OHG, declared bankruptcy about one year later when the Taiwanese parent enterprise stopped all funding, resulting in extensive redundancies. This led to speculation in the German media that Siemens had off-loaded the division to avoid dealing with the fallout of its imminent demise. At about the same time, Siemens' Supervisory Board increased the salary of the Siemens Board of Directors by 30%. In an attempt at damage limitation over the following negative publicity, the board pledged their pay rises to a relief fund set up by Siemens to aid the workers affected.
In 2006, a series of corruption charges were laid against Siemens. Kleinfeld, along with other former Siemens executives and board members, was "accused of failing to prevent corruption". In September 2009, Siemens extended an offer to Kleinfeld and other former members of "its Managing Board against whom damages are being claimed ... to declare their willingness to reach a settlement." While Kleinfeld denied wrongdoing and no charges were brought, he agreed to pay an undisclosed sum to settle the matter.
Kleinfeld is a member of the board of directors of Alcoa Inc., of Bayer AG and of Citigroup Inc. After the announcement that he would be joining Alcoa, he resigned from the Citigroup board as Alcoa’s then CEO was the lead director for the board.
- Corporate Identity und strategische Unternehmensführung, Akademie-Verlag München 1994, ISBN 3-929115-16-6
- "Meet Klaus Kleinfeld". Reuters. Retrieved 08 April 2013.
- Alcoa: News: News Releases: Klaus Kleinfeld Elected Alcoa President and Chief Operating Officer
- "Alcoa posts its third consecutive quarterly loss", CNNMoney.com
- CEO Compensation for Klaus Kleinfeld, Equilar.com
- Siemens Goes Mega - TIME
- The World from Berlin: Siemens Strikes Back - International - SPIEGEL ONLINE - News
- Siemens supervisory board plans to up 2007 management board salaries by 30 pct - Forbes.com
- Siemens offers former Managing Board members until mid of November 2009 to indicate willingness to settle corruption damages
Heinrich von Pierer
|CEO of Siemens AG
2005 – 2007