Hleb has been a leading transfer target for Barca over the summer and a deal is now close to being finalised.
The Belarusian revealed last week that 'serious negotiations' were underway with Barca after he had become 'tired' of living in London.
He is due to arrive in Barcelona on Wednesday lunchtime before being put through a series of medical tests throughout the day.
The Spanish giants have confirmed on their official website that, providing Hleb passes his medical, he could sign his contract within 24 hours.
No details of the fee agreed between Barca and Arsenal have been disclosed, nor the length of contract Hleb has been offered.
Skysports.com revealed last week that the former Stuttgart schemer was close to securing his exit from Emirates Stadium.
Hleb joined Arsenal in an £11.2million deal in 2005 and he has scored 10 goals in 130 appearances for the club.
Gunners boss Arsene Wenger has already brought in a replacement for Hleb in the guise of Samir Nasri and has also been linked with a move for Liverpool midfielder Xabi Alonso.
sat bye bye to Hleb!!
welcome alonso!! it time to dump rafa and join the wengers!!
Finally this deal will come to an end tomorrow... Next up... Adebayor, Barry, Ronaldo and Lampard... This year transfer period really have a lot of problems...