It was used moments after Portugal appeared to break the deadlock in 21 minutes, and resulted in the goal being ruled out.
There was much confusion on the pitch following the ball hitting the back of the net as the Portugal players gathered in a huddle to celebrate.
But replays showed the VAR system did indeed get the decision right, despite taking a frustratingly long time to reach a verdict.
The passage of play came about following a Cristiano Ronaldo free-kick, which slammed into the Mexico wall standing just in front of the area.
The deflected ball was looped back into the box, where four Portugal players – including Pepe – appeared to be in offside positions.
The linesman didn’t raise his flag however, and the Real Madrid defender managed to knock the ball back into the path of Ronaldo, who had a shot at goal.
The 32-year-old saw his effort smash against the crossbar before landing at the feet of Andre Gomes, who took a first time shot.
The volley bounced towards the goal at speed – it’s too hard to know whether it clipped Nani’s head en route – before crossing the line.
Immediately after the goal was scored the camera zoomed in on Pepe celebrating, as if he was the goal scorer, although replays showed he was nowhere near the ball before it hit the back of the net.
The Portugal players then set about celebrating together before the referee stopped them in their tracks and referred the goal to the VAR.
After more than 30 seconds the missed offside was brought to his attention and the goal was ruled out.
Here’s how some spectators reacted to the drama: