The former Liverpool star says “it’s a dream come true” to move to the Nou Camp after securing the £142million switch yesterday.
He also told Barcelona supporters that he looks forward to seeing them at his unveiling tomorrow.
Coutinho will also hold a press conference where he will speak to the world’s media.
But he gave fans a brief message ahead of the big day.
“Hi Barca fans, I’m already here,” Coutinho said on Barcelona’s Instagram account.
“It’s a dream come true.
“I hope to see you tomorrow.”
Coutinho was briefly shown to the press following Barcelona’s 3-0 victory against Levante today.
He appeared in the media room at the Nou Camp dressed in a Barca hoody and posed for photos.
But fans will have to wait until tomorrow for the full formalities of his transfer to be completed.
Coutinho is expected at the Nou Camp at 12pm where he will meet president Josep Maria Bartomeu and sign his contract at 12:30pm.
At 1pm, Coutinho will join president Josep Maria Bartomeu and vice president Jordi Mestre for a photo.
Coutinho is scheduled to be presented in front of the fans on the pitch at 1.30pm.
And the final part of the day will see Coutinho speak to the media at a press conference at around 2.15pm.