"We must focus our capital and resource on those customers, services and geographies that can truly benefit from our future investment," group chief executive officer Jeff Gravenhorst said in a statement.
ISS, founded in 1901, operates in 74 countries and is one of the world's largest private employers with some 500,000 employees on its books.
The firm, which posted revenues of 80 billion kroner (10.7 billion euros) in 2017, plans to withdraw from 13 markets by 2020, raising 2.5 billion kroner, Danish media reported.
ISS will focus its withdrawal on emerging markets, led by eastern Europe, pulling out of Estonia, the Czech Republic, Hungary, Romania, Slovakia and Slovenia, as well as Thailand, the Philippines, Malaysia, Brunei, Brazil, Chile and Israel.
The divested businesses currently employ 100,000 of its 490,000 staff.
Spokesman Rajiv Arvind stressed the workers affected by the news were not losing their jobs but remained employed in those subsidiaries being sold off.
For Sydbank analyst Mikkel Emil Jensen, ISS was reacting to the arrival of more and more small-scale entrants to the sector.
"It is easy for new competitors to enter this market. You get a bucket and sponge and you can offer the same thing as ISS," Jensen told the Ritzau news agency.
ISS shares were down 2.6 percent in Copenhagen early afternoon.