When Leicester striker Kelechi Iheanacho ran onto a Riyad Mahrez pass to slot home in the 77th minute of the third round replay, his strike was initially ruled out for offside.
But after a short delay while the attack was being analysed by the VAR assistant Mike Jones, the decision was changed – replays showed Nigeria’s Iheanacho was just onside – and referee Jon Moss awarded a goal.
The VAR system was first used in England earlier this month for Brighton’s FA Cup third round tie against Crystal Palace and the League Cup semi-final first leg between Chelsea and Arsenal.
However, this was the first time it had actually been needed to reverse a decision.
“I didn’t know if I was onside or offside but I agree totally now that I was onside,” Iheanacho said.
“I was concentrating on the goal, I didn’t think if I was onside or offside but Riyad told me that I was onside.
“We just waited to see what the decision was.”
Leicester striker Jamie Vardy added: “This man got the goals and has shown that VAR does work.”
Former Manchester City youngster Iheanacho had already put Leicester ahead in the 43rd minute at the King Power Stadium, running onto Islam Slimani’s pass and firing home.
Leicester’s reward for a comfortable win against their third tier opponents is a trip to Peterborough, also of League One, in the fourth round.
VAR, which has already been used in other competitions around the world, can be called on to rule over goals, straight red cards, penalty decisions and cases of mistaken identity.
Elsewhere, Cardiff set up a fourth round clash with Premier League leaders Manchester City as the Championship side won 4-1 in their replay at fourth tier Mansfield.
With City boss Pep Guardiola watching from the Field Mill stands, Bruno Manga put Cardiff ahead in the 34th minute.
Danny Rose equalised for Mansfield 60 seconds later.
But Neil Warnock’s side dominated in the second half and Junior Hoillet put them ahead in the 66th minute.
Anthony Pilkington made it three after 71 minutes and Hoillet’s second in the 89th minute ensured City will visit south Wales on January 28.
West Ham needed a goal late in extra-time from Reece Burke to clinch a 1-0 win over third tier Shrewsbury at the London Stadium.
Hammers boss David Moyes suffered one of the worst defeats of his career at the hands of Shrewsbury when he was in charge of Everton.
But Moyes avoided more FA Cup misery against the minnows thanks to young defender Burke, who slammed in his first goal for the club with only eight minutes left before a penalty shoot-out.
In the fourth round, West Ham will play Wigan or Bournemouth, whose replay is set for tomorrow (Jan 18).
Championship sides Reading, 3-0 winners against Stevenage, and Sheffield Wednesday, who beat Carlisle 2-0, will meet in the fourth round.