Barry had been in exile since the start of July when Martin O'Neill fined him for criticising the Villa manager's refusal to let him join Liverpool in a Sunday newspaper article.
The 27-year-old was frustrated after O'Neill turned down a series of bids from Liverpool and missed Villa's pre-season training camp in Switzerland following his suspension.
A move to Anfield appears no closer as Villa hold out for an 18 million pounds (22.6 million euros) fee, although Arsenal have entered the race.
But O'Neill has opted to allow his star player to rejoin the squad and Barry could even be involved in Villa's Intertoto Cup clash against Danish side Odense on Saturday.
"The club can confirm that Gareth Barry will be back in training at Bodymoor Heath tomorrow (Wednesday)," a statement on Villa's website read.