The home side laid siege to the Torquay goal for long periods of the second half before a defensive slip-up from veteran Paul Warhust let Lee Thorpe in to send the travelling Gulls fans delirious.
Torquay boss Ian Atkins handed starts to seven of his 11 summer signings with Nathan Abbey, Mickey Evans, Lee Andrews, Lee Mansell, Stevland Angus, Lee Thorpe and Stephen Reed all making debuts for the Seasiders.
For Barnet, Lee Harrison was the only new name to feature in the starting line-up, returning to the side as cover for injured goalkeeper Ross Flitney just three years after leaving Underhill.
The game got off to a sluggish start with both sides failing to settle down in their first game back after the summer break.
Torquay winger Martin Phillips looked the liveliest player on the pitch in the opening exchanges.
Both sides began to rely on the long ball as a route to goal and it nearly paid off for Barnet when Liam Hatch forced the ball into the net only for the goal to be disallowed for pushing on Torquay keeper Nathan Abbey.
In the closing stages of the first half Torquay began to pick holes in the Bees' midfield, Martin Phillips turning Adam Gross inside out and whipping in another teasing cross only for Mickey Evans to head straight into the arms of Lee Harrison.
The second half saw the home side crank up the pressure with lively Bees' winger Dean Sinclair orchestrating proceedings.
The introduction of Tresor Kandol and Magno Vieira saw Barnet come close to breaking the deadlock on several occasions with Kandol - recently released from prison - seeing a goal-bound drive acrobatically palmed away by Abbey.
With Barnet camped inside the visitors' area pushing for a 90th minute winner, former Aston Villa winger Jamie Ward broke for Torquay before playing a through-ball towards Lee Thorpe. Paul Warhust comfortably intercepted, but when his back-pass to Harrison was under-hit, Thorpe sneaked in, rounded the keeper and reeled away in celebration.