The detainees were greeted by Qatari and US officials as they arrived at Doha International Airport.
Five US detainees have flown out of Iran today in a swap for five Iranians held in the US.
The rare deal has been brokered by Qatar between the enemies that also unfroze $6bn of Tehran's funds.
A Qatari plane took off from Tehran carrying the five detainees and two of their relatives after the US and Iran received confirmation that the funds had been transferred to accounts in Doha, according to a source cited by Reuters.
The funds were blocked in South Korea after US sanctions on Iran were toughened in 2018.
Qatar will ensure the money, which is now available to Tehran, will be spent on humanitarian goods and not items under US sanctions.
An Iranian official said the five Americans, who have dual nationality and are due to fly to the US, are in "good health."