Mooar was part of the Crusaders coaching team from 2015 to 2019 during their unbroken seven-year Super Rugby title-winning streak.
He has spent his time since then coaching teams around the world, adding a World Cup and Six Nations tournament under his belt.
He was head coach at Scarlets in Wales and then assistant coach of Scotland.
Mooar will be with the Crusaders for the next two seasons until 2026.
"My family and I are really happy to be back in Christchurch, and I’m really excited to be at Rugby Park again," said Mooar.
"It feels like coming home.
"It’s wonderful to be back in the mix with the players and staff, and I’m looking forward to connecting with the community again."
Said Penny: "Brad has some awesome credentials. He is a quality coach and a quality human being.
“He has a proven success record and is going to offer the coaching group and the organisation a wealth of experience and knowledge."
Assistant Crusaders coach Matt Todd was part of the playing squad when Mooar was previously with the Crusaders.
Sai Mooar: "It’s cool to be back working with some superb people that I’ve worked with previously, as well as building relationships with those I hadn’t met before."
Crusaders chief executive Colin Mansbridge was "really pleased" to have Mooar back.
"He is vastly experienced," Mansbridge said.
"He is really invested in the Crusaders, and I’m really pleased to have someone of his calibre on board to compliment the group that has grown enormously since last year.”
