Deacon, who injured his calf during Gloucester's loss to London Irish on Sunday, has been ruled out of action for at least two weeks.
The loss of Deacon meant that Gloucester were forced to look for extra cover, with England stars Phil Vickery and Trevor Woodman and Argentina's Rodrigo Roncero all away on World Cup duty.
Olver, who makes the move form Worcester, can play on both sides of the scrum and has plenty of experience in the Zurich Premiership – having spent some time at Harlequins and Saracens.
"We were already stretched in the front row department and following Andy Deacon's injury we have had to move quickly to sign up Adrian," said Nigel Melville, Gloucester's Director of Rugby.
"Every team has to have cover in the front row. We've lost a lot of players to the World Cup and we were always going to have to have a bit of luck with injuries. Unfortunately this hasn't been the case, but Adrian has experience and will offer us options for this weekend."