Early career

Indongo debuted professionally at the age of 25, on 25 July 2009, with a points decision (PTS) win over Pohamba Mandume. After winning his first six fights, he won his first regional title, the Namibian lightweight title, by defeating Samuel Kapapu, and retained it against Peter Malakia.

After improving to 14 consecutive wins, he won the WBO Africa light-welterweight title in October 2012 via victory over James Onyango. Indongo went on to make six successful defenses of that title between 2014 and 2016. Indongo was a late bloomer on the world stage, with his first world title fight taking place when he was 33. His trainer, Nestor Tobias, stated that he often needed to be more aggressive and "deliver the killer punch".^[3]

Unified light-welterweight champion

In October 2016, undefeated IBF and IBO light-welterweight champion Eduard Troyanovsky (25-0, 22 KOs) stated he would make a voluntary defence on the Lebedev-Gassiev card in Russia on 3 December.^[4] On 7 November, Indongo, who was ranked WBO #3, WBA #15 and IBF #10, was announced as his opponent, for the fight to take place in Moscow, in his first bout held outside of Namibia.^[5] Despite being a favoured underdog, Indongo knocked out Troyanovsky after only forty seconds of the first round with a left hook, becoming Namibia's fourth world boxing champion. Troyanovsky was badly hurt from the shot and did not get up. Referee Mark Calo-Oy immediately halted the fight with Troyanovsky still down on the canvas. After some assistance, they eventually got Troyanovsky back to his feet and took him out of the ring.^[6][7]

In late December, there were talks for a potential unification fight between Indongo and WBA champion Ricky Burns.^[8][9] On 9 January, Burns' manager Tommy Morrison confirmed a deal was being put together for Burns to fight Indongo in a unification fight in April at The SSE Hydro in Glasgow.^[10][11] On 11 January, Sky Sports confirmed a deal was reached for Burns and Indongo in a unification title bout on 15 April 2017. The WBA, IBF and IBO titles would be at stake.^[12][13] This was Scotland's first ever unification fight.^[14][15] Burns failed to become Scotland's first unified world champion when he lost via a one-sided unanimous decision with wide scores of 120–108, 118-110 and 116–112. In the last two rounds, Burns hit the canvas three times, but these were ruled as a slip. Following the defeat, Burns praised Indongo, "He was so so awkward. He was a lot better than we thought he was going to be. He can hit as well." He also said that he wouldn't retire.^[16][17]

Career from 2018

On 5 January 2018, Lou DiBella of DiBella Entertainment announced that he had signed Indongo on a long-term promotional contract.^[27] A few hours later, Nestor Tobias, Indongo's manager and promoter from Namibia claimed that Indongo and DiBella had breached contract. Tobias stated that Indongo was under contract with his MTC Nestor Sunshine Boxing & Fitness Academy until 2020.^[28]

The WBC super lightweight title became vacant after Terence Crawford decided to move up to welterweight. It was announced that number 1 ranked Amir Imam would fight number 3 ranked Jose Ramirez for the vacant title. WBC President Mauricio Sulaiman then announced that Viktor Postol, who was ranked number 4, would fight number 2 ranked Regis Prograis (20-0, 17 KOs) for the interim WBC title. The winner of both fights would then meet to become the full titleholder.^[29] In January 2018, a deal was finally reached for the fight between Postol and Prograis to take place on 9 March at the Buffalo Run Casino in Miami, Florida.^[30] On 12 February, ESPN reported that Postol suffered a fractured thumb and forced to drop out of the bout. Indongo was announced as his replacement, with the bout still taking place on 9 March, however the venue was changed to Deadwood Mountain Grand, a casino and resort in Deadwood, South Dakota, with Showtime televising the bout live.^[31] Prograis knocked Indongo down four times in the fight, dropping him once in round 1 and three more times in round 2 before referee Ian John Lewis stopped the fight at 2:54 of round 2. Indongo started the fight well before being hit with a hard jab that dropped him. Indongo was hurt with this shot. Indongo fought close to Prograis, which seemed to benefit Prograis. After the fight, Prograis told Showtime's Steve Farhood, "After the first round, I felt his punches. He couldn't punch. He couldn’t hurt me. I got a little reckless. But I got the job done, so I can’t complain." Prograis landed 46 of 94 punches thrown (49%) and Indongo connected on 32 of his 120 thrown (27%).^[32]

Indongo came back with a win against Carltavius Jones Johnson in his next fight. Indongo was controlling the action in round one. In round two, Jones Johnson fought more aggressively, but a counter right hook from Indongo dropped him on the canvas. Johnons managed to beat the count, but the referee decided he was not fit to continue, awarding Indongo with the TKO win.^[33]

On 27 November 2020, Indongo faced Daniyar Yeleussinov. Yeleussinov looked dominant and dropped Indongo in the opening round. It looked like the fight would end in the opening round, but Indongo managed to survive to the round. In the second round, Indongo was dropped again, and again managed to beat the count. He did not look fit to continue however, and the referee waved the fight off right after the knockdown.^[34]