Carroll has not played for the Hammers this season and has spent time in Holland and Belgium recovering from a double fracture in his right foot.
Carroll told his club's official website: "I am so happy to be back here at the training ground around all the lads.
"You don't realise how much you miss all the banter and other stuff until you are away from it, so it's great to be here again.
"I flew back a few times during my treatment to watch matches and catch up with my family, team-mates and friends, but now I'm back for good.
"It has been a long, hard process but now I can see the light at the end of the tunnel. It felt great to be out on the pitch jogging and kicking a ball in the open air, even if it was a bit cold!
"It's been really hard watching the games while I've been out. We haven't picked up the results we have deserved, so I can't wait to get out there again and start helping the team to win some games."
Hammers boss Sam Allardyce will be desperate for the club's £15million record signing to return after watching his side slide deeper into relegation trouble after a 1-0 defeat at Crystal Palace on Tuesday night.
But despite the mounting pressure Allardyce has insisted he will not rush Carroll back into first-team action, saying last week: "We can't get over-anxious and push him too hard.
"We need to get him fit to stay fit. Not fit to a point where he might pick up another injury. That's what we have to be careful about."