McCullum's knock was the highest in T20 international history, and coming from just 58 balls, made him the only player in the history of the format with two international centuries.
His innings beefed up the Kiwis' innings to an imposing 191 for three from their 20 overs, and in response Bangladesh could not compete, losing early wickets and falling well short on 132 for eight.
New Zealand sprung a surprise by opting to pair all-rounder James Franklin with Martin Guptill at the top of the order.
A relatively sedate start from the Kiwis, having been put in by Bangladesh, saw Guptill depart, bowled through the gate by Abdur Razzak.
And while Franklin struggled to find rhythm, McCullum, the leading scorer in T20 history, set to work.
He was busy from the off, adding impetus as Franklin struggled.
Bangladesh had tried seven different bowlers by the 13th over, but McCullum was well into his stride by his point, reaching his 50 from just 29 balls.
Franklin began to open up, but holed out to Mashrafe Mortaza at midwicket with 35 to his name.
It mattered little – McCullum was taking plenty of the strike, and scoring so quickly that captain Ross Taylor, normally a huge hitter in his own right, was left to play the foil role.
McCullum thundered orthodox sixes down the ground and over cow corner, as well as some extraordinary strokes, such as a cross-batted swat of a Mortaza bouncer, straight over the bowler’s head for a maximum.
His ton came from 51 deliveries, and by the time he was dismissed from the final ball of the innings, the match already looked out of Bangladesh’s reach.
And so it proved when the men in green came out to chase. Kyle Mills accounted for dangermen Tamim Iqbal, Shakib Al Hasan and Mushfiqur Rahim in his first three overs, before Mohamed Ashraful followed, trapped on the back foot by Tim Southee, leaving Bangladesh stumbling at 37 for four.
Nasir Hossain was the only Bangladesh batsman to offer any meaningful resistance, finishing with 50 from 39 deliveries after faring well against spinners Daniel Vettori and Nathan McCullum.
But the game was out of range long before the end of the innings, and it was a painfully one-sided match which already puts Bangladesh’s tournament at risk. Even defeating Pakistan in their final group game may not be enough if results do not go their way, as their net run rate will be hurt by this one-sided defeat.
New Zealand, however, have one foot in the next round, and look to have the firepower required to make an impact in a wide-open competition.