A left-handed batsman, Fleming made his Test debut in March 1994 against India winning the Man of the Match award on debut after scoring 92. In 1995 he survived controversy when he was caught and admitted to smoking marijuana with teammates Matthew Hart and Dion Nash while on tour at their hotel. In England's tour of New Zealand in 1996/7 he scored his maiden Test century in the First Test at Auckland. In the Third Test of the tour he took over the captaincy from Lee Germon becoming New Zealand's youngest captain at 23 years and 320 days.

Fleming became New Zealand's most successful captain in September 2000 with a victory over Zimbabwe. This was the 12th win under his captaincy overtaking Geoff Howarth. Fleming was long regarded as an underperformer with the bat, with one of the worst 50 to 100 conversion ratios in world cricket. However since the 2003 tour of Sri Lanka, Fleming has silenced his critics, with 274 not out against Sri Lanka - when Fleming selflessly declared rather than staying to reach 300 which would have been a record in New Zealand cricket history.