The winner will be announced in London on October 26, with Kane entering the race after a prolific campaign for Bayern Munich and England in which he scored 73 goals in 61 appearances.
However, Beckham has opted for Messi, pointing to the Argentine's influence at the 2026 World Cup and his continued success with Inter Miami.
Messi scored eight goals as Argentina reached the World Cup final, where they were beaten by Spain, and Beckham believes the veteran forward's performances at the age of 39 were particularly significant.
"When you see him do things like this, when you see him have the World Cup that he's had, it's not luck that he's being considered for the Ballon d'Or again," Beckham said on Apple TV.
"He was probably the best player in the tournament. He had an incredible year last year.
"He came into that tournament, 39 years old, to affect a World Cup and every game the way he did. That's special. There's no one at 39 that's doing that and doing it at that level.
"So he deserves to be considered for the Ballon d'Or. He, in my opinion, should win it."
Messi has also continued to make an impact at club level since joining Inter Miami in 2023.
He reached 100 goals for the MLS side during Wednesday's 2-0 victory over Cruz Azul in the Campeones Cup, scoring the opener before setting up Casemiro for the second goal.
The victory secured Inter Miami's first Campeones Cup title, adding to the club's first MLS Cup triumph last year.
Beckham, who is a co-owner of Inter Miami, acknowledged the strength of the competition for this year's award, naming Kane alongside Kylian Mbappe and Jude Bellingham.
"When you're talking about Leo, I'm his biggest supporter," the former England captain added.
Casemiro, who scored from Messi's corner against Cruz Azul, also backed his team-mate.
"He's still the best," the Brazilian said. "He proved it at the World Cup and he's still proving it in the MLS."
Messi has already won the Ballon d'Or eight times, with his previous triumphs coming in 2009, 2011, 2012, 2013, 2016, 2019, 2021 and 2023.
He now faces competition from a group that includes Kane, Mbappe, Bellingham and other leading names when the 2026 winner is announced later this year.
Bukayo Saka has admitted England are still carrying the pain of their dramatic World Cup semi-final defeat to Argentina as they prepare to face Spain in the Nations League.
Lisandro Martinez has called on Argentina to put their World Cup final disappointment aside as they prepare for a special night honouring Lionel Messi.
Kylian Mbappe has described the prospect of playing under Zinedine Zidane for France as a remarkable full-circle moment, recalling that the legendary midfielder was already part of his football journey when he was a teenager.
Lamine Yamal believes winning the 2026 FIFA World Cup with Spain and helping Barcelona retain La Liga has put him in the strongest position to win the Ballon d'Or.
