With a knee injury ruling Tom Brown out until October, and Tim Visser and Dougie Fife primed for international duty in the autumn and spring, head coach Alan Solomons has sought to deepen the club's wing reserves.
He said: "We're pleased to welcome another fine, young, international athlete into the Edinburgh Rugby squad.
"Injuries and Scotland duty means we are stretched for specialist wingers going into the season, and this addition relieves the pressure on the squad in that area.
"Brett [Thompson] has already showcased his talent on the international stage and we believe there is much more to come from the him, which is exciting for the competition in our squad."
Thompson's route to professional rugby started aged 12, with encouragement from Irish father and former USA internationalist, Salty Thompson, who now coaches the country's U20 squad.
After representing USA U18 and U20, Brett was recruited by his University to play two seasons at defensive end for the Arizona Wildcats, in front of crowds of up to 50,000.
He then returned to his first love and made an immediate impact on the HSBC Sevens World Series, playing in 14 tournaments, before making a try-scoring debut in his country's 38-35 win over Canada in Sacramento last month.
Thompson - who will check in to BT Murrayfield tomorrow (Wednesday) - said: "I can't wait to get started with Edinburgh Rugby.
"It's always been a dream of mine to play at the top level. I'm ready to work hard and compete to help the team be successful in any way I can."
Brett Thompson (23), wing
Born: 17 August 1990
Height: 6'4"; weight 100kg, 15st 10lb
Honours: USA (1 cap), USA 7s (14 HSBC Sevens World Series tournaments)
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