Rotorua Lakeside Charitable Trust chairman Ian Edward was delighted the Koi Boys had joined the line-up.
"We are thrilled for him [Ngatai] in that he has always wanted to come back and perform before his home crowd and family."
The Koi Boys shot to fame in last year's TV reality show The Voice Australia and recently released their first album in New Zealand.
"Last year's Lakeside was hugely successful and the inclusion of the Koi Boys will ensure that the crowd numbers will exceed those that we have ever hosted previously," Mr Edward said.
He said the event had a "star-studded" cast, with international tenor Simon O'Neill, crowd favourite Jason Kerrison and the "ever popular" Annie Crummer.
There will also be a performance by aerial ballet troupe from Auckland The Dust Palace, featuring Rotorua's Eve Gordon.
Music will be provided by the Auckland Philharmonia Orchestra conducted by Guy Noble.
Mr Edward said Lakeside was a family concert spectacular which aimed to provide something for everyone.
He said the fact the event was now in its 21st year would suggest the Rotorua public looked forward each year to enjoying an international standard concert.
Organising committee member Trevor Maxwell said they were "absolutely chuffed" to have secured the Koi Boys.
Mr Maxwell said he had seen Ngatai growing up and he was thrilled he would be gracing the Lakeside stage.
