The 20-year-old, who arrived in London on Monday, has turned down a contract extension with the Brazilian outfit and has already posted a farewell message to his boyhood club.
"If my cycle in Sao Paulo closes, gratitude is undoubtedly the word that stays, it's been six years of a lot of learning and work," Luizao posted on Instargam.
"I arrived a dreamy boy and left the club as a man with goals and goals to be met, I know many will judge the form I leave but I make it clear that above all I maintain my respect and love for the club. Thank you Sao Paulo Football Club."
Sao Paulo head coach Rogerio Ceni confirmed last month that the defender is expected to leave the club when his deal expires on January 31.
"Luizao is very likely to leave," Ceni told reporters. "Not that the club wants it, but because of the player's desire. The contract is expiring in January. We will have some departures and changes. It's part of (football). It's a painful process."
According to Sky Sports News, via West Ham Zone, Luizao has completed his medical with West Ham and has agreed to sign a three-and-a-half-year contract until 2026.
The report adds that Luizao is expected to join up with the Hammers' development squad and is regarded as a prospect for the future.
Luizao has enjoyed an impressive breakthrough year with Sao Paulo in 2022, featuring in 26 first-team matches across all competitions.
The Brazilian has now decided to make the next step in his career and will hope to make immediate impression under David Moyes, who has been hampered with defensive injuries so far this season.
Kurt Zouma is currently sidelined after undergoing knee surgery at the end of last month, while Nayef Aguerd missed the first three months of the season with an ankle problem and has since picked up a knee injury on World Cup duty with Morocco.
In addition, Angelo Ogbonna has been gradually eased back into the first-team fold following nine months out with an ACL injury, while the long-term future of Craig Dawson is believed to be uncertain as the 32-year-old is said to be eyeing a move away from the London Stadium.
Luizao is set to become West Ham's first signing in January, but they are set for more transfer business in the winter window as 90min reports that the Hammers are also interested in Sao Paulo's 20-year-old midfielder Pablo Maia, although they face competition from Tottenham Hotspur for his signature.
Elsewhere, Bayer Leverkusen and two unnamed Premier League clubs have allegedly expressed their interest in signing right-back Vladimir Coufal ahead of the winter window.