Brendon McCullum played 3 under-19 Test matches for New Zealand in 2000/01 and scored 455 runs at 151.66 with 3 hundreds. The runs were made in quick time too, coming at a strike rate of 95.58 runs per 100 balls. In July 2002 while playing club cricket in Australia for Northern Territory side Palmerston Cricket Club, he scored a record 250 not out in less than 100 balls. It is believed to be the highest ever score made in the territory.

In 2004 he played in a Test series against England and scored what was then his highest score, an innings of 96 at Lord's. His maiden Test century came several months later when he scored 143 against Bangladesh. He fell just short of his second Test hundred in a game against Sri Lanka but instead scored his second 90 when dismissed one short of his hundred. His second century would later come with a run a ball 111 against Zimbabwe.