Danish-British security services group G4S bought ISS, a cleaning services company, in a deal worth 8.2 billion U.S.dollars on Monday.
That corresponds to 130 Danish kroner (around 24.2 dollars) per share, ISS said in a press statement.
The new entity will have more than 1 million employees in over 130 countries. It will be listed on both the London and Copenhagen stock exchanges.
According to ISS, the deal presents strong global growth opportunities for both companies, especially as they share cultural and industrial values.
"Together we can increase our exposure to significant growth opportunities in emerging markets, and accelerate our efforts in finding integrated solutions," ISS Chairman of the Board Ole Andersen said in the statement.
Top management for the new entity will come from G4S, where CEO Nick Buckles and CFO Trevor Digthorn continue in their positions, while ISS CEO Jeff Gravenhorst will be responsible for Europe operations.
According to Gravenhorst, ISS has enjoyed 4 percent annual, average, organic growth since the beginning of 2005, and 7 percent growth in the third-quarter of 2011.
ISS had a turnover of 57.8 billion Danish kroner (10.8 billion dollars) in the first 9 months of the year, with an operating profit of 2.9 billion Danish kroner (around 540 million dollars).
The deal means G4S and ISS now comprise the world's largest security services and cleaning-and-facilities management company.