The Manchester City forward underwent surgery in February for a stress fracture sustained while on loan at Everton last season.
Before he was sidelined, Grealish had enjoyed a promising loan spell at Goodison Park, making 22 appearances under David Moyes as he looked to recapture the form that helped City win the Treble.
While his former England team-mates prepared for their tournament opener against Croatia in Dallas, Grealish was simply grateful to be back on the grass at Everton's Finch Farm training ground.
The 30-year-old shared the moment on social media, posting pictures of himself back in training kit for the first time in months.
"Ahhh man can't even explain how good this felt! 5 months ago since I last put my boots on.. Back on the grass today!"
Grealish added that the moment marked an important step in his recovery.
"Best feeling ever man. Time to get ready!!"
No decision has yet been reached over Grealish's long-term future, with the England international not expected to confirm where he will play next season for some time yet.
His continued rehabilitation at Everton is understood to be part of an ongoing good relationship between player and club, rather than a sign of where his future lies.
Moyes was quick to defend Grealish towards the end of last season after images emerged appearing to show the midfielder asleep at a table surrounded by drinks, with the Everton manager stressing the positive influence the loan spell had brought to his squad.
"I only think of Jack as being positive. He has done great for us. He was brilliant for those 20 games or however many it was."
Moyes went on to praise the wider impact Grealish had on the team's performances before his injury.
"I think when I look back at the season, how controlled the team was, how well we played, he was really good for us. So I only think of him positively. He has had a bit of time off because he's healing from his foot injury."
Grealish's recovery comes at a difficult time personally, with the World Cup now under way without him for the first time since his senior England career began.
His return to full training will nonetheless be seen as a significant marker, with City and Everton both expected to discuss his next move once his rehabilitation is further along.