The purchase brings the number of S-61s purchased by the State Department to 29.
"The S-61 helicopter is known as an industry workhorse and for decades has reliably performed missions for U.S. and foreign allied militaries," said S-61 Programs Director John Johnson.
"The upgraded S-61helicopter can be outfitted to meet a wide variety of requirements, and we believe it provides 'best-in-class-value' for a mid-size, multi-mission helicopter."
The three aircraft will transport diplomatic personnel in Iraq and Afghanistan.
Building on the S-61 helicopter's 50-year legacy of dependability, SAS initiated the S-61 upgrade program in early 2010.
As Sikorsky's launch customer, the State Department has entered into a five-year indefinite-quantity agreement with the option to purchase up to 110 upgraded S-61 aircraft.
The IQ purchase agreement serves as the contracting vehicle for any U.S. government agency to purchase upgraded S-61 aircraft.
Sikorsky said the upgraded S-61 helicopters will undergo a full structural refurbishment with all major dynamic components zero-timed and key upgrades provided, including new composite main rotor blades and a survivability suite.
Sikorsky Aerospace Services is the aftermarket division of Sikorsky Aircraft Corp.