The 71-seat turboprops will be delivered over two years starting next March and join 45 other of the planes in service.
Flybe, which is undergoing a restructuring, also said it was terminating its order for 20 E-175 jets, while delivery of four other planes jets is being deferred until 2018.
"We are committed to flying the right aircraft on the right routes," stated Flybe CEO Saad Hammad.
Following a strategic review last year, the airline unveiled a plan to fly regional routes with larger aircraft and seat capacity.
Eleven of 35 E-175 planes with 88 seats ordered in July 2010 are already in service.
The Republic Airways fleet switch comes as its holding company removes its 31 Q400s as part of a deal announced Wednesday to buy 50 E-175 regional jets valued at US$2.1 billion from the Brazilian airplane maker.
The U.S. company, which has indicated that its large CSeries order no longer fits into its original regional fleet plans, said the remaining Republic Q400s will be sold, leased or returned to the lessor.
Deliveries of Republic's new Embraer 76-seat jets will begin in July 2015.
The planes will be operated by its Shuttle America subsidiary for United Airlines under the United Express brand.
The order is in addition to one signed by Republic in January 2013 for 47 E-175s, of which 34 have been delivered. Republic also has 32 options for the planes.
The Indiana-based holding company that owns Chautauqua Airlines, Republic Airlines and Shuttle America was one of the first U.S. carrier to fly Embraer E-Jets in 2004.
Republic will operate a fleet of 223 Embraer planes.
The American company said in May it was concerned about the slow sales of Bombardier's new jetliner but had no plans to cancel its order.
Republic CEO Bryan Bedford said prior to an engine failure that grounded flight testing for more than three months that he wasn't upset by delivery delays of a plane that has "game-changing technology" being proven through flight testing.
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