Former reality TV star Trump is known to make visitors flinch with a strong handshake that he often combines with a wrench of the arm to leave his victim off balance.
But Macron, France's 39-year-old political wunderkind, appeared to be ready for him when they met for lunch at the US embassy in Brussels ahead of a NATO summit.
As the world cameras watched, Macron held on tight to Trump's notorious power grip as the two men sat next to each other, the Frenchman's mouth clenched and eyes firmly fixed at the tycoon's squinted stare.
Watch: Trump 'pushes past' Montenegro PM
Their knuckles then appeared to turn white with their jaws clenching and faces tightening.
The moment - finally - broke off, and the men left the scene to enjoy a quick meal of veal fillet with Belgian chocolate mousse for dessert.
But the two presidents were not finished.
Later at NATO headquarters Macron was the last to turn up for the opening of the alliance's new headquarters and found himself again shaking hands.
Cue laughs from leaders including German Chancellor Angela Merkel and NATO chief Jens Stoltenberg as Macron found his arm wrenched about by a smiling Trump.
It is not the first time Trump has caught the world's attention with his macho man grip.
Watch: Trump lectures NATO nations on spending
His handshake style came under media scrutiny after a meetings with the Japanese and Canadian leaders.
Thursday's family portrait at NATO was also notable for Trump apparently pushing aside the prime minister of Montenegro, Dusko Markovic, in order to get in the front row.
Among Trump's critics was British author J.K. Rowling - the creator of Harry Potter.
"You tiny, tiny, tiny little man," she tweeted, providing a GIF of the incident.
Montenegro will formally become NATO's 29th member on June 5, the alliance announced on Thursday, amid bitter Russian opposition to the move.
