Beale's return at full-back after recovering from a shoulder injury was one of two changes to the starting line-up from the team which beat the Six Nations champions 25-23 courtesy of Mike Harris's late penalty last week to take a 2-0 lead in the series.
Sitaleki Timani also returns to the side to win his third cap after missing the first two Tests with injury, replacing Rob Simmons in the second row alongside Nathan Sharpe, who will win his 105th cap.
Beale, who has been in fine form this season at fly-half for the Melbourne Rebels, was selected despite being charged with assault after a fracas at a nightclub before Australia's 27-19 victory in the first Test in Brisbane.
Beale and fly-half Quade Cooper, who was ruled out of the series as he continues to recover from the injury he suffered at last year's World Cup, are also the subject of an Australian Rugby Union investigation into the incident.
"It has been frustrating for Kurtley, and he's obviously had some off-field challenges to deal with as well, but it was important for all concerned that he had full confidence in his shoulder before we looked at re-introducing him to the Test arena," Deans said.
Winger Cooper Vuna makes way for his Super Rugby team mate in the back three with the versatile Adam Ashley-Cooper moving from full-back to take Vuna's place out wide.
"It's been a while now after injuring my shoulder and just very excited about the opportunity to play an exciting team like Wales. I'm raring to go," said Beale.
Beale said he was happy to play any position for his country, while Deans said the flexibility of his backline meant the 23-year-old would turn up in the fly-half position at some point in the Test.
"You see the way we play the game, we structure opportunities for skill-sets of the blokes we've got. So there's no doubt you'll see Kurtley at first receiver on occasions," he said.
"Kurtley's done a great job at full-back, we're lucky to have blokes that are that versatile."
Simmons is relegated to a bench packed with five forwards, while last Saturday's Melbourne hero Harris and Vuna, who was cleared to play after escaping further punishment for tackling Leigh Halfpenny in the air last weekend, miss out altogether.
"Wales are a very good side. They give you nothing and they take their scoring chances. They showed that in the Six Nations, and they showed it again last weekend," Deans added.
"Both games in the series to date have been very close, there's no reason to suggest that Saturday afternoon will be any different.
"They will be absolutely desperate to end on a high, and will know that they are capable of doing exactly that. We must similarly raise the level of our game if we are to deny them."
Team: 15-Kurtley Beale, 14-Adam Ashley-Cooper, 13-Rob Horne, 12-Pat McCabe, 11-Digby Ioane, 10-Berrick Barnes, 9-Will Genia; 8-Wycliff Palu, 7-David Pocock (captain), 6-Scott Higginbotham, 5-Nathan Sharpe, 4-Sitaleki Timani; 3-Sekope Kepu, 2-Tatafu Polota-Nau, 1-Benn Robinson.
Replacements: 16-Stephen Moore, 17-Ben Alexander, 18-Rob Simmons, 19-Dave Dennis, 20-Michael Hooper, 21-Nic White, 22-Anthony Fainga'a