The 22-year-old former Peterborough striker is the Bees third signing of the summer and will wear the Barnet number 11 shirt.
Shaq came through the Spurs Academy and had various loan spells at Leyton Orient, Torquay, Southend, York and Wigan.
The Posh signed Coulthirst in January 2016 where he made 35 appearances. At the start of this year, he joined Mansfield on loan scoring 5 goals in his 15 appearances.
Speaking about his latest addition, Rossi Eames has said “Firstly, he fills the number 11 shirt which everyone has waited for.
“He fits the culture and philosophy we want to play with, on and off the ball.
“He’s flexible with regards to the fact he can play in both a front three and in a front two, he also offers pace, aggression and can score goals”
Everyone at The Hive would like to welcome Shaq to the club!