Firmino’s 100th minute goal secured a 1-0 victory for Jurgen Klopp’s men in the Khalifa Stadium in Doha Saturday to win a competition that had seen them beaten in previous finals three times, including by Flamengo in 1981.
Brazilian star Firmino, who had seen an earlier second half effort rattle the post, finished confidently after a fine move involving Jordan Henderson and Sadio Mane.
Flamengo might have equalized in virtually the final action of the match, but substitute Lincoln blazed over from close range.
But overall, European champion Liverpool deserved its victory, which might have been secured earlier after initially being awarded a 90th minute penalty in normal time.
Mane looked to have been tripped by Flamengo defender Rafinha as he was about to shoot, but on VAR review Qatari referee Abdulrahman Al Jassim overturned his original decision.
Any sense of injustice felt by Liverpool was quickly dispelled by Firmino’s clinical strike, receiving Mane’s pass before twisting and turning to beat Flamengo goalkeeper Diego Alves.
Firmino had also scored the winner in Liverpool’s 2-1 win over Monterrey, the Mexican side taking third in the competition by beating Al Hilal on penalties after it ended 2-2 in normal time.
Klopp had welcomed back Dutchman Virgil van Dijk after the key defender sat out Wednesday’s semifinal due to illness and his side threatened to overwhelm the Rio-based side with a fast start.
Firmino, Naby Keita and Trent Alexander-Arnold all came close for Liverpool in the first six minutes before Flamengo recovered its poise and made some threatening attacks.
Bruno Henrique, troubling Alexander-Arnold with his blistering pace, saw an effort deflected wide and the first half ended with the Brazilians matching Liverpool.
But after the break Firmino should have opened the scoring after latching on to another superb Henderson pass, his volleyed effort hitting the inside of the post and going clear.
At the other end, Liverpool goalkeeper Alisson made a fine stop from Flamengo striker Gabriel Barbosa before Alves tipped away a net -bound Henderson strike.
Then came the penalty controversy, referee Al Jassim leaving fans puzzled and also rescinding a yellow card for Rafinha.
Nine minutes into extra time, Firmino finally settled an entertaining affair to complete Liverpool’s global trophy haul after two losses in finals of the old Intercontinental Cup and another to Sao Paulo in the 2005 Club World Cup final.
“We kept going until the end and got the goal in extra time, said skipper Henderson.
“We’ve found a way for a long time now, some late goals. We just want to keep our feet on the ground and keep going.”