Daniels will replace Phil Gifford from July 13.
Gifford is leaving Newstalk ZB Afternoons after two years co-hosting the show with Barnett.
"When we launched the show, I couldn't have wished for a better partner than Phil to get things up and running. He's a true mate and has been an absolute rock," said Barnett.
Daniels brings extensive experience in corporate and community leadership and governance alongside his broadcasting background to support the network producers' plans to steadily evolve the show for listeners.
"For the last four decades I've worked with and represented communities I've lived in, which has given me a very clear sense of what really matters to people, the things they care about, want to be heard on and want to talk about. There's no better place to have those conversations with Kiwis than Newstalk ZB Afternoons," said Daniels.
Simon Barnett said: "Both being Christchurch-based broadcasters for so many years, James and I know each other well. But, in the all the years we've had on air we've always worked on opposing networks. Now, to not only be on the same network, but to be hosting a show together, it's going to be a real treat for me and ZB's listeners."
While Daniels has been able to manage his community commitments with the Coast role, the Newstalk ZB afternoon show conflicts with meeting schedules so he will resign from Christchurch City Council as soon as the 2021-2031 Long Term Plan has been approved in late June.
"It has been an honour to be elected by the people of the Coastal ward, which is where I've grown up and live. I trust they're happy with my efforts and feel they've had a strong voice in the Council Chamber."
James Daniels will continue to host Canterbury Mornings on Coast then go nationwide with Simon Barnett on Newstalk ZB Afternoons.
• Newstalk ZB Afternoons with Simon Barnett and James Daniels, Tuesdays to Fridays 12pm-4pm – from July 13, 2021