Ihimaera's new novel, The Torwenna Sea, is set in Tasmania during the 1840s and details the lives of Maori transported there as convicts.
But The Whale Rider author has acknowledged some passages in the book were not credited.
In a written apology, Ihimaera said he had been working with his publisher to contact the authors whose work he did not acknowledge to apologise for the oversight.
Penguin publishing director Geoff Walker said the book would not be withdrawn from sale and the publisher was standing by the novel.
He declined to say how the plagiarism was identified. Ihimaera said that less than 0.4 per cent of the 528 page novel had been published without acknowledgement, he said. "I am deeply sorry and take full responsibility for this oversight," he said.
"The authors I have managed to contact understand how it occurred and have accepted my apologies. The passages in question will be fully acknowledged in a future edition of the book," Ihimaera said.
Ihimaera is also a Professor of English and is a Distinguished Creative Fellow in Maori Literature at the University of Auckland.
Dean of Arts, Associate Professor Jan Crosthwaite, said the plagiarism had been investigated by the university and said there was no deliberate wrongdoing.
