"We are excited to have secured New Zealand's best to lead business for the future."
O'Sullivan will work across all NZME business brands and platforms including digital, publishing, radio and events.
She will also work closely with The New Zealand Herald Business Editor Liam Dann and NZME Radio's general manager talk, Dallas Gurney.
O'Sullivan said she was thrilled with the appointment.
"I have a passion for high-quality business journalism and the opportunity to take a hands-on role working collaboratively with NZME's talented team across the whole business is too good to miss."
O'Sullivan launched the annual Mood of the Boardroom report and the annual China Business Summit.
She is also a multiple winner of the Westpac Financial Journalism Award and the Qantas Reporter of the Year.
NZ Herald Editor Shayne Currie said O'Sullivan was one of New Zealand's most highly respected business journalists and one of the Herald's best read.
"Fran and Liam make for a formidable duo," he said.