The Sixers took to their social media channels to post a photo of James' blue jersey hanging in a locker stall along with a crown as a nod to his "King James" nickname.
"I cannot wait to see LeBron alongside Jaylen Brown, VJ Edgecombe, Joel Embiid, Tyrese Maxey, and our talented roster as we work to deliver a championship for Philly," Sixers Managing Partner Josh Harris said in a press release.
"To LeBron and his family: we are grateful you chose the 76ers, and look forward to this next chapter of your legendary career. Welcome to the 76ers!"
James, 41, announced his decision to join Philadelphia last Friday and will now look to become the first player to win NBA championships with four different teams after lifting two titles with the Miami Heat and one each with the Cleveland Cavaliers and Los Angeles Lakers.
The four-time NBA Most Valuable Player, who has worn both No. 23 and No. 6 during his professional career, spent the last eight seasons with the Lakers, leading them to a title in 2020 after two separate stints with the Cavaliers and four years with the Heat.
In announcing what he called his "last decision", James said he opted to sign with Philadelphia because he felt he could make them a championship team. The Sixers have not won an NBA title in 43 years.
"There is no doubt LeBron is one of the greatest players to ever play the game of basketball and there are no words to measure the impact he’ll have on this organisation,” said Sixers President of Basketball Operations Mike Gansey.