In 2005, ISS A/S was acquired by funds advised by EQT AB and Goldman Sachs Capital Partners, and delisted from the Copenhagen Stock Exchange.

The next year, the second-largest acquisition in company history was made when ISS acquired the outstanding 51% of the shares in Tempo Services in Australia.

In 2007, it expanded its portfolio in the United States through the acquisition of Sanitors Inc.[citation needed] By 2010, ISS's revenue had passed 70 billion DKK and it total number of employees had reached 500,000.

[16] In April 2017, ISS announced that it had acquired US catering services company Guckenheimer with an annual revenue of approximately DKK 2,300 million and 3,200 employees in 33 US states.

[17] The company signed its largest customer agreement in its history in 2017 with Deutsche Telekom, covering approximately 9,000 sites across Germany, more than 6,000 employees and about 4% of Group revenue.