The pre-tournament favourites stretched their unbeaten run to 36 games on Wednesday in Abu Dhabi, with Messi looking good amid a host of warm-up matches before the Qatar tournament.
Messi scored his team's fourth goal right before the break, having also set up Julian Alvarez to open the scoring in the 17th minute. Angel di Maria scored twice in between.
Argentina coach Lionel Scaloni made four changes at halftime but opted against resting his star player Messi.
Inter Milan forward Joaquín Correa scored the visitors' fifth goal on the hour mark.
Argentina start their World Cup against Saudi Arabia on November 22 before also facing Mexico and Poland in Group C.
"We're confident," midfielder Rodrigo De Paul said.
"But for many it will their first World Cup so the first game will be very important."
Tunisia, Australia's second opponents in Group D, continued their preparations behind closed doors in Doha with a 2-0 win over Iran.
Naim Sliti netted a 62nd-minute penalty after a handball from Iran's Abolfazl Jalali, who was sent off, and defender Ali Abdi added a second seven minutes later.
Iran open their Group B campaign against England on Monday while Tunisia's first game is on Tuesday against Denmark.
In Muscat, Niclas Fullkrug scored on his Germany debut as the four-time World Cup champions earned a 1-0 win over Oman.
Fullkrug's introduction for the second half brought a new dimension to an attack that had failed to spark before the break.
Youssoufa Moukoko struck the post on his Germany debut right before halftime.
The 17-year-old Moukoko was Germany's youngest debutant since Uwe Seeler, who was younger by 16 days in 1954.
Moukoko then made way at the break for Fullkrug, with the 29-year-old forward almost scoring early in the second half only to be denied by a good save from the impressive Ibrahim Al-Mukhaini.
Oman sub Muhsen Al-Ghassani somehow missed with the goal at his mercy in the 72nd and the hosts were to rue the miss when Kai Havertz set up Fullkrug to score the winner in the 80th.
In Warsaw, Robert Lewandowski watched from the bench as Poland edged Chile 1-0 in a bruising encounter thanks to a late goal from Krzysztof Piatek.
Lewandowski didn't play but will likely start Poland's tournament-opening game against Mexico on November 22.
Andrej Kramaric's late goal was enough for 2018 finalists Croatia to beat Saudi Arabia 1-0 in Riyadh.
Croatia star Luka Modric played only the last 25 minutes, enough to set up Kramaric for the winner in the 82nd.
In Girona, a goal and an assist from Mattias Svanberg led Sweden to a 2-1 win over Mexico.
The CONCACAF powerhouse, who will be competing in their eighth straight World Cup, will arrive in Qatar on Thursday with plenty of work to do before kicking off their campaign against Poland on November 22. They also face Argentina and Saudi Arabia in Group C.
With Reuters.
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