He is considered one of New Zealand's most successful batsmen and captained the side to the finals of the 2015 Cricket World Cup and 2009 ICC Champions Trophy.

[14] On 3 March 2008, before facing England for the test series, McCullum was involved in the State Shield Final versus the Auckland Aces, scoring 170 runs for the Otago Volts to help beat the Aces at Eden Park's outer oval, and helped to chase down a daunting total of 7 for 310, he broke multiple State Shield batting records.

While playing for Warwickshire in the 2015 T20 Blast McCullum hit what was at the time the highest score in England's domestic T20 cup, 158* from just 64 balls.

On 1 July 2008, McCullum scored his maiden ODI century, a 135-ball 166, against Ireland in the Associates Tri-Series in Scotland.

On 6 November 2009, against Pakistan at Abu Dhabi, McCullum scored his second ODI century of 131 to elevate New Zealand to 303 and win the match to level the series.

On 27 February 2010, McCullum became the second player to score a T20I hundred, finishing 116 not out, one run short of Chris Gayle's record of 117.

He shared a 352 run partnership with BJ Watling, then a record sixth wicket stand,[28] rescuing New Zealand from a likely innings defeat.

[30] Two years after his debut as NZ captain, in which the team was bowled out for a paltry 45, Black Caps returned to respectability.

On 13 December 2014, McCullum was named New Zealander of the Year by the New Zealand Herald beating out stiff competition from Lane Pilkington due to his continued co-operation with ICC over the match-fixing scandal which resulted in Chris Cairns being charged for lying to court, and also for changing the perception of the Black Caps as easy-beats.

While he got a 2-ball duck on a green pitch and three errors as a fielder, he was given a key to Wellington, a symbolic equivalent of "Honorary Citizen", in recognition of his heroics the previous year, becoming the third person to receive the honour after Wellington-born Sir Peter Jackson and Sir Richard Taylor, who were recognised by the city for their work on the Lord of the Rings movies.

McCullum led the New Zealand team to their first World Cup final, scoring timely innings in the pool match against Australia and South Africa in the semi-final.

His aggressive starts against the strike bowlers of the opposition team such as James Anderson, Mitchell Johnson, and Dale Steyn favoured the rest of the players to play their natural game.

On 22 December 2015, McCullum announced his intention to retire from international cricket at the end of the southern summer in his home test against Australia, rather than after the 2016 ICC World Twenty20.

He hit his 102nd career six to surpass Adam Gilchrist as the most prolific six-hitter in test cricket.

[37] In September 2018, he was named as the Icon Player for Kandahar's squad in the first edition of the Afghanistan Premier League tournament.

[38] In July 2019, he was selected to play for the Glasgow Giants in the inaugural edition of the Euro T20 Slam cricket tournament.

He has the ability to play the Dilscoop (which was invented by Sri Lankan Tillakaratne Dilshan) or precisely the ramp shot, which involves the batsman squatting down and scooping deliveries back over the wicketkeeper's area.

Playing this ramp shot in a Twenty20 International match on 28 February 2010 in Lancaster Park, against Australia, he managed to hit Shaun Tait for two sixes in an over back over Brad Haddin's head, forcing Australia to set a back stop (the fielder near the boundary behind the wicketkeeper or first slip) in his final test match.

He also likes to cut, cover drive, or advance the wicket to punch the ball up for boundaries from a batting stance standing on or outside leg stump.

McCullum had to decide whether to play for New South Wales, KKR, or Otago in the 1st edition of the Champions League Twenty20.

But by late 2013, McCullum's recurring back problems meant he can no longer perform wicketkeeping duties effectively, he gave up his gloves to Ronchi in ODIs and T20s, and McCullum became a middle order batsman, or as a cover for opening the batting in tests, having batted at 1,2,5–7 in his career, while his fielding position becomes predominantly mid-off, mid-on or mid-wicket, and in his final international matches, he ended at first slip after the injury to Ross Taylor.

In the 2015 Queen's Birthday Honours McCullum was appointed an Officer of the New Zealand Order of Merit for services to cricket.

[53][54][55] The South Africa cricket team toured England to play three Test matches in August 2022.

In September 2024, it was announced that in addition to his duties with the Test side, McCullum would take over as coach of the England limited-overs teams in January 2025.

[61] McCullum was hesitant to respond to criticism and defended his actions, but in 2016 apologised for the incident when he delivered the MCC Spirit of Cricket lecture.

"[64] During the 2009 ICC Champions Trophy, he was again involved in a controversial run out, this time dismissing England's Paul Collingwood after he had left the batting crease at the conclusion of an over.

[66] In July 2023, during the second Ashes Test at Lord's, McCullum, who was England's head coach, was critical of Australia's wicket-keeper Alex Carey for running out Jonny Bairstow in similar circumstances.

[67][68][69][70][71] McCullum has since been involved in setting up CricHQ with the company's CEO Simon Baker and former New Zealand cricketer Stephen Fleming.

The cricket competition management software and live scoring platform manages the administration of cricket test countries New Zealand, Sri Lanka, South Africa and Zimbabwe with 49 of 105 national governing bodies also use its services from club level upwards.

The Problem Gambling Foundation made a formal complaint about a YouTube advertisement he appeared in promoting the website, saying it would be illegal if it was shown on a New Zealand content provider.