The companies are Aerotron and LH Colus.
Aerotron will supply the ballistics protection, while LH Colus will provide seating and stretchers for the aircraft, which is being built for the Brazilian air force.
"We are quite pleased to announce another two Brazilian companies as suppliers of the KC-390 program", said Eduardo Bonini Santos Pinto, vice president of Operations and chief operating officer of Embraer Defense and Security.
"Both companies bring to the program excellent solutions and we are certain that they will deliver technologically advanced products of the highest quality."
Aerotron said its initial prototypes of ballistics protection will be delivered to Embraer next year. LH Colus will develop and deliver the first set of seats and stretchers for the KC-390 test flights scheduled to begin in 2014.
The KC-390 is a medium-sized, jet-powered aircraft that will be used for cargo, troop transport, aerial refueling and other missions.