Australia thumped Namibia by nine wickets at the Sir Vivian Richards Stadium, North Sound, Antigua, on Wednesday.
Chasing a target of 73 runs, Australia raced to victory in 5.4 overs and also qualified for the Super 8 stage of the event.
David Wiese picked up Namibia's only wicket after sending David Warner, who scored 20 off 8, back to the pavilion.
Travis Head remained unbeaten on 34 runs in 17 balls with the help of five fours and two sixes.
Earlier, Australia cleaned up Namibia for only 72 runs after deciding to bowl first.
Leg-spinner Adam Zampa became the first Australian men's cricketer to take 100 wickets in T20I cricket after bagging figures of 4-12 in four overs.
"To get the win tonight and qualify for the Super Eights, that is a nice feeling," Zampa said after being named Player of the Match.
"I bowled a couple of pies tonight but in general, the ball feels like it is coming out well. Being encouraged to pick up wickets in the middle, particularly by the captain.
"We are happy, it is the first step in trying to take the trophy home but a long way to go."
Pacer Josh Hazlewood claimed two wickets for 18 runs in four overs as Australia dominated proceedings with the ball. Marcus Stoinis also chipped in with a couple of wickets as Namibia were bundled out in 17 overs.
Namibia captain Gerhard Erasmus, who took 17 balls to get off the mark, was the highest run-scorer with 36 runs in 43 balls with the help of four fours and a six.
Apart from Erasmus, Michael van Lingen was the only batter who got into double figures with 10 runs.
This was the first competitive T20I between Australia and Namibia. But they played each other in a warm-up game before this tournament, with Australia registering a convincing seven-wicket win.
Teams:
Namibia: Nikolaas Davin, Michael van Lingen, Jan Frylinck, Gerhard Erasmus(c), JJ Smit, Zane Green(w), David Wiese, Ruben Trumpelmann, Bernard Scholtz, Jack Brassell, Ben Shikongo.
Australia: Travis Head, David Warner, Mitchell Marsh(c), Glenn Maxwell, Marcus Stoinis, Tim David, Matthew Wade(w), Pat Cummins, Nathan Ellis, Adam Zampa, Josh Hazlewood.