The two new aircraft are Global 6000 surveillance planes, while the old planes to be upgraded are part of the UAE's fleet of Saab 340s, said Major General Abdullah al-Hashimi at a joint press conference at the Dubai Airshow.
The date of delivery has not been finalized, but could be within two years, he said, adding that the purchase “supports surveillance capabilities” of the Gulf nation's Air Force.
The UAE has been part of the US-led coalition bombing militants of the Islamic State group in Iraq and Syria.
It has also played a key role in the Saudi-led coalition that launched a military campaign in March against Iran-backed rebels in Yemen.
Saab is one of the world's leading defence and security companies and has around 14,700 staff around the world.
The firm reported soaring annual profits in 2014 and forecast stronger arms sales this year in response to conflicts in the Middle East and Ukraine.
The UAE's purchase comes hot on the heels of a high profile deal between the Swedish company and Brazil, which is set to buy 39 Jas Gripen aircraft.
The Brazilian federal government and Saab officially signed the contracts a year ago, after 12 months of negotiations. Brazilian prosecutors then looked into the deal after the price tag rose due to fluctuating exchange rates and shifting requirements. However the South American country's President confirmed last month that it would still go ahead at a cost of 39 billion kronor ($4.7 billion).