"We've been testing the concept with our readers and had excellent feedback that demonstrates a clear demand for a weekday compact.
"The new design allows us to improve the way we integrate and deliver weekday news and information across both the compact format and our digital offering, nzherald.co.nz."
The Weekend Herald - judged New Zealand's best newspaper at the recent Canon Media Awards - will remain as a broadsheet format, a size that is more suited to a leisurely read on Saturdays.
Before the change in September, the New Zealand Herald will continue to consult readers, advertisers and other stakeholders to test design concepts, new content development and integration with existing digital platforms.
"We are committed to the ongoing delivery of quality journalism and the new format allows us to explore creative ways of delivering New Zealanders the news and information they require," said Mr Simons.
"We look forward to revealing the new-look weekday Herald in September and marking another important milestone in the New Zealand Herald's 150-year history."
The exact launch date and details of new content and design will be announced soon.