Early career Kambosos made his professional boxing debut in May 2013, aged 19, when he faced Filipino fighter Jayson Mac Gura and was victorious via a second-round technical knockout. In December 2016, he captured the WBA Oceania title by beating world number nine Brandon Ogilvie. He then went on to face
Qamil Balla in May 2017, whom he defeated by unanimous decision in a ten-round fight. Five months later, he knocked out
Krai Setthaphon in the ninth round and won the WBA Oceania and IBF Pan Pacific titles in the lightweight division.
Pacquiao's sparring partner In June 2017, Kambosos was tabbed by Manny Pacquiao as his main sparring partner in preparation for
the fight with Jeff Horn and has remained Pacquiao's main sparring partner for his fights after Horn as well. In April 2018, Kambosos signed a promotional contract with DiBella Entertainment. In May 2018, he made his debut in the US and knocked out Jose Forero in just 1 minute and 48 seconds. On 19 January 2019, Kambosos defeated Rey Perez at
The MGM Grand in
Las Vegas on the undercard of
Manny Pacquiao vs
Adrien Broner via unanimous decision in his second fight on US soil. On 7 June in Athens, Kambosos returned to his native land of Greece and knocked out Venezuelan 11–2 (9 KOs)
Richard Pena in round six in front of the packed out
Galatsi Olympic Hall. He called out former two division world champion
José Pedraza after his victory.
Rise up the ranks Kambosos vs Bey On 14 December 2019, Kambosos faced his toughest opponent yet, former IBF lightweight champion
Mickey Bey. He won the bout by
split decision on the undercard of
Terence Crawford vs
Egidijus Kavaliauskas. Scorecards read 97–92, 96–93 and 94–95 in favour of Kambosos.
Kambosos vs Selby On 31 October 2020, Kambosos defeated former IBF featherweight champion
Lee Selby by split decision at
The SSE Arena in London. Selby was ranked #1 by the WBO, #4 by the IBF and #12 by the WBC at the time. The win over Selby made Kambosos the
mandatory challenger for the IBF lightweight title.
Unified lightweight champion Kambosos vs López On 9 January 2021, the
IBF ordered undefeated unified lightweight champion
Teofimo Lopez to defend his titles against Kambosos, their number one contender and mandatory challenger. The fight was initially set for 5 June 2021 at the
LoanDepot Park in
Miami,
Florida, before being postponed multiple times, due to complications involving López contracting
COVID-19, and disputes over the venue of the fight. The fight had gone to purse bids which was won by
Triller with a winning bid of over US$6 million. However, on 6 October, it transpired that the IBF had found Triller in
default of its contract obligation to stage the fight, and that its rights would be awarded to the second highest bidder,
Eddie Hearn's Matchroom, and the fight was shown live exclusively on the streaming service
DAZN. Both fighters each traded a knock down but ultimately Kambosos won the bout via split decision to become the new unified lightweight world champion. One judge had it 114–113 for López, while the other two judges scored the bout 115–112 and 115–111 in favour of Kambosos.
Kambosos vs Haney On 5 June 2022, Kambosos Jr. and
Devin Haney clashed at
Marvel Stadium in
Melbourne, Australia to determine the 1st undisputed
lightweight champion of the four-belt era. The fight did not proceed without controversy, as Kambosos was unable to make weight on his first attempt. He initially weighed in at 135.36 lbs, 0.36 lbs over the 135 lb limit for the lightweight division. On his second attempt an hour later, within the two-hour limit, Kambosos weighed in at 134.49 lbs. The fight then proceeded as planned and Kambosos was defeated by Haney after a unanimous decision, with two judges scoring the fight 116–112 and one judge scoring it 118–110, all in favor of Haney. The deal for the fight included an automatic rematch clause which Kambosos exercised. The rematch occurred on October 16, 2022, in Australia.
Kambosos vs Haney II George Kambosos and Devin Haney met in their rematch at
Rod Laver Arena in Melbourne, Australia on October 16, 2022. Kambosos lost the fight via unanimous decision with the scores of 118–110 (twice) and 119–109, in favor of Haney.
Lomachenko vs. Kambosos On May 12, 2024, in Perth, Western Australia, Kambosos fought
Vasiliy Lomachenko for the vacant IBF lightweight title. Lomachenko defeated Kambosos by TKO in the 11th round by bodyshot. This was after Kambosos went down to a bodyshot earlier in the round and took a standing eight count. Kambosos' corner threw in the towel after the second knockdown before the referee waved off the fight.
Kambosos vs. Wyllie Kambosos was scheduled to face
Daud Yordan at the Qudos Bank Arena in the Sydney Olympic Park on March 22, 2025. At the beginning of the fight week it was announced that Yordan withdrew due to medical reasons, and was replaced by Jake Wyllie. ==Professional boxing record==