The Sydney-based franchise confirmed that Beale would return to his hometown club on a one-year deal following his release by the Melbourne Rebels last month.
Beale was expected to make a return to the Waratahs after the Rebels decided to cut ties with the 24-year-old following a campaign overshadowed by off-field controversy.
Beale was sent home from a tour of South Africa and suspended for four games after an altercation with team-mates Gareth Delve and Cooper Vuna before seeking counselling for alcohol-related issues.
He returned in time to play in Australia's 2-1 series defeat to the British and Irish Lions, when his missed penalty in the opener in Brisbane cost the Wallabies victory.
Since then McKenzie has taken charge of the national team, following Robbie Deans' exit, and has welcomed a change of scenery for a player who has won 39 caps for his country.
"It's really good news for Australian rugby and great news for the Waratahs, he's a high-quality player," McKenzie said.
"Given the Waratahs brand of football, he'll really add to the mix there.
"I'm looking forward to having him back playing his best footy, that's obviously a good thing for the Wallabies."
Beale admitted he was looking forward to returning to the Waratahs, where he made his debut in 2007 before moving south last year.
"I feel at home in Sydney, it's where my family is," said Beale, who is sidelined for the rest of the year following shoulder surgery.
"I'm really looking forward to playing some good, consistent rugby. I've made the decision to get my shoulder right, I hope next year will be a big one for me.
"I'm excited by the Rugby World Cup on the horizon and I'm just looking forward to getting back to playing really good rugby, having a big year for the Waratahs and hopefully getting selected for the Wallabies."
He added of his Waratahs return: "I'm really excited to be coming home and to be playing under Michael Cheika and the coaching team at NSW.
"The Waratahs are a team going places."
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