With the game seemingly heading to a 1-1 draw, the Brazilian forward produced a moment of real quality in the 90th minute, powerfully heading home from a corner to fire the visitors to a 2-1 victory.
Although still early in the season, the result could prove pivotal in the title race, with both sides battling it out for the top spot ahead of kickoff.
The win now moves the reigning champion three points clear of its rivals, as it laid down a marker to the rest of the league.
Speaking after the match, Liverpool boss Jurgen Klopp said his side deserved the late winner and praised Firmino for just his third league goal of the season.
“It was a really, really good game from us. It’s exactly the way you have to play. You have chances, you score the goal,” Klopp told BBC Radio 5 Live.
“I love talking about Bobby’s [Firmino] goals but it always sounds like we are shocked […] it’s not that rare that he scores.
“He’s a top-class player and he scores goals but he has some things to do for us which sometimes keep him outside of the box for us. I couldn’t be more pleased for him and for us because it was a top goal and very important.”
‘The best team lost’
Liverpool is now unbeaten in its last 66 league games at Anfield, but it could have easily lost that record on Wednesday.
As expected, Jose Mourinho set his side up to punish Liverpool on the counterattack and his game plan almost paid off.
Steven Bergwijn hit the post and Harry Kane missed from close range in a dramatic few minutes in the second half, but the visitor was left to rue the missed opportunities.
“So close to winning, not so close to a draw,” a visibly frustrated Mourinho told Amazon Prime after the match.
“We missed the chances, we had the chances, had the game under control. A draw would be a bad result so you can imagine how we feel with a defeat.
“Very good performance, of course some mistakes, some things to improve, a very unfair result.
“Today, Liverpool didn’t look like a team that is champion, European champion, world champion. That difference was not on the pitch.”
As the referee blew the full-time whistle, cameras showed Mourinho and Klopp involved in a touchline exchange that seemingly ended amicably.
When asked what was shared, Mourinho said he had told Klopp that the “best team lost” and questioned the German’s animated antics on the touchline.
“He [Klopp] disagreed, but that’s his opinion,” Mourinho added.
The 73-year-old is credited with transforming the club during his successful reign, winning a treble in the 2000-01 season.
Liverpool now faces a tough test away to Crystal Palace next in the Premier League whilst Spurs host Leicester City.