The 25-year-old ruptured the anterior cruciate ligaments in his right knee during Argentina's preparations for the FIFA World Cup in Russia and underwent surgery in June.
Since then he has spent three months in recovery in Barcelona but he has returned to London to begin his programme of rehabilitation with West Ham's medical team.
Richard Collinge, head of medical at West Ham, told the club's official website: "We're really pleased for Manu and it's great to have him back.
"He's now at the three-month stage, so I flew out to see Manu and his consultant Dr Cugat at the weekend and the doctor is very happy with his progress after three months.
"Rehab-wise, we have a plan in place and Manu is very disciplined and very motivated and we're moving in the right direction."
In Lanzini's absence West Ham have endured a torrid start to the season, losing all four of their Premier League matches and scoring just two goals.
Ahead of their return to domestic action against Everton on Monday (AEST), Collinge had good news for boss Manuel Pellegrini regarding Andy Carroll and Winston Reid.
"Andy Carroll is progressing really nicely and he's going to start doing some work on the pitches this week," said Collinge.
"Winston Reid is in a knee brace and he's eight weeks down the line from his surgery and making good progress.
"He's going to be a little bit longer, but he's also making good progress."