The aircraft will be manufactured at a Boeing plant in St. Louis, Missouri and are expected to be delivered to Qatar by the end of 2022.
"This contract provides for the foreign military sales requirement to procure 36 new F-15QA aircraft for the Qatar Emiri Air Force," the Pentagon said in a statement.
The contract's announcement is likely to be welcomed by the Qatari government and comes amid an ongoing diplomatic row between Qatar and a number of its Gulf neighbors, including Saudi Arabia, Bahrain and the United Arab Emirates.
The countries accuse Qatar of supporting terrorism, a charge Doha denies.
President Donald Trump initially appeared to back Saudi Arabia in the dispute, saying in June that "the nation of Qatar unfortunately, has historically been a funder of terrorism at a very high level."
However, Trump appeared to change course just days later, offering to help the parties resolve their differences during a call with the Qatari emir.
"If I can help mediate between Qatar and in particular, the UAE and Saudi Arabia, I would be willing to do so," Trump said in September while appearing alongside the emir of Kuwait.
Secretary of State Rex Tillerson traveled to the region in July in an attempt to mediate the dispute between the US allies but was unable to achieve a rapprochement.
Speaking about the diplomatic row while in Washington last month, Qatar's foreign minister, Sheikh Mohammed bin Abdulrahman Al Thani, said Trump "wants to see an end for this," and praised Qatar's relationship with the US.
The US military maintains a significant presence in Qatar, using the Al Udeid Air Base to oversee air operations in the region, including the air campaigns against ISIS and the Taliban.