At the 2011 European Championships in June he beat the German Eric Brechlin 23:16 and the Irishman Cathal McMonagle 22:10 but was stopped by the Romanian southpaw Mihai Nistor after receiving several standing counts.

En route to the final, Joshua secured his place at the 2012 Olympic Games in the super-heavyweight division as a relative newcomer to the elite level of the sport.

[15] In his next bout he fought 2008 Beijing Olympics silver medalist Zhang Zhilei, dropping his taller opponent in the middle round; Joshua won by 15:11 guaranteeing at least a bronze medal.

Joshua made his professional debut on 5 October 2013 at the O2 Arena in London in the Main-Event of a card featuring Scott Quigg's successful WBA (Regular) super-bantamweight title defence against Yoandris Salinas, beating Italian Emanuele Leo by a technical knockout (TKO) in the first round.

The following month, on the undercard of Ricky Burns against Terence Crawford, Joshua defeated Hector Alfredo Avila with a first-round KO, in Glasgow, Scotland.

[27] He was supposed to face American boxer Kevin Johnson on 31 January 2015 at The O2 Arena in London, but the bout was cancelled after Joshua sustained a back injury.

[33][34] On 16 July 2015, it was announced that Joshua would fight undefeated Scottish boxer Gary Cornish (21–0, 12 KOs) for the vacant Commonwealth heavyweight title at The O2 Arena, London, on 12 September.

[62] WBA president Gilberto J. Mendoza confirmed that the winner will have to face mandatory challenger Luis Ortiz next, with deadlines due to be set after the unification fight.

[70] In January 2017, Eddie Hearn announced that over 80,000 tickets had been sold, a new box office record, overtaking Carl Froch vs. George Groves II.

[87][88] As a result, on 4 August, upon learning that Klitschko had retired, the IBF immediately ordered Joshua and 36-year-old Kubrat Pulev (25–1, 13 KOs) to fight next, with a deal needing to be reached by 3 September 2017.

[89] The WBA then ordered Joshua to make his mandatory defence against their top ranked fighter Luis Ortiz, giving them 30 days to reach a deal.

[93] Promoter Eddie Hearn made the official announcement on 5 September, "I'm delighted that we will be in Cardiff at the magnificent Principality Stadium for the next step of the AJ journey.

[97] The injury was later revealed to be true and 36-year-old Carlos Takam (35–3–1, 27 KOs), who was ranked number 3 by the IBF, stepped in to replace Pulev on 12 days notice.

Eddie Hearn said in a statement that he received a phone call from Pulev's promoter Kalle Sauerland advising him of a shoulder injury he had sustained during sparring.

[120] On 14 January, negotiations came to a close and the fight was officially announced to take place on 31 March in Cardiff, live on Sky Sports Box Office.

[144] On 16 July, Joshua vs. Povetkin for the WBA (Super), IBF, WBO, and IBO heavyweight titles was officially announced for 22 September on Sky Box Office.

[158] Whilst still waiting for Hearn to contact him, Whyte claimed to hear rumours that Joshua would drop the Wembley date and instead fight American contender Jarrell Miller at Madison Square Garden.

[183] On 1 May, with one month to go before fight night, Joshua vs. Ruiz was confirmed and announced to take place at Madison Square Garden in New York City exclusively on DAZN in the US.

On the night, Joshua boxed a disciplined fight, keeping Ruiz at a distance with his jab and using lateral movement to avoid trading punches up close as he had in their first encounter.

[93][99] On 2 March 2020 it was announced that Joshua would defend his heavyweight titles against Pulev (28-1, 14 KOs), who was IBF mandatory challenger, at London's Tottenham Hotspur Stadium on 20 June.

[202] As a result of these developments, on 21 May the WBO gave Joshua's camp 48 hours to come to an agreement for the fight with Fury, or they would instead order a bout against their mandatory challenger, former undisputed cruiserweight champion Oleksandr Usyk.

Krassyuk noted that Usyk relished the prospect of squaring off against Joshua twice: "So I remember when we discussed with Oleksandr the issue of rematch, he was delighted and said 'Wow, cool, I will beat Antokha [sic] twice.

[217] In the first pre-fight press conference on 9 February, Joshua announced his new partnership with American trainer Derrick James, as well as being questioned by his promoter Eddie Hearn on his motivation for fighting.

Despite a particularly cautious start to the fight, he made use of his jab to set up power punches with his right hand, prevailing via unanimous decision, with judges' scorecards of 117–111 (twice) and 118–111 in his favour.

[230] In October 2023, reports stated that Joshua could potentially face Deontay Wilder on 23 December on the same card alongside Tyson Fury and Oleksandr Usyk in Saudi Arabia.

[244] Joshua is recognised as one of the most marketable athletes in the world, and has lucrative endorsement deals with numerous brands, including Under Armour, Beats By Dre, and Lucozade.

[245] Joshua has spoken of his ambition to surpass Floyd Mayweather Jr.'s reported career earnings of $700 million, saying in an interview with GQ, "When I first started, the aim was to become a multi-millionaire.

[259] In June 2020, Joshua was accused of racism by some social media users for his speech at a Black Lives Matter protest in Watford, where he said "show them where it hurts, abstain from spending your money in their shops and economies, and invest in black-owned businesses."

Joshua was suspended from the GB Boxing squad and was sentenced to a 12-month community order and 100 hours' unpaid work after pleading guilty at crown court.

[272][271] In an interview with iFL TV in July 2014, Joshua named Muhammad Ali, Mike Tyson, Larry Holmes, Lennox Lewis, and Evander Holyfield as his top five greatest heavyweight boxers of all-time.