He said his new role was "a real opportunity to continue working with local businesses and help them achieve their goals and aspirations".
"It has been very rewarding seeing the Rotorua business community and economy growing and Rotorua is punching above its weight.
"I wish the chamber all the best for the future."
Chamber president John McRae said Mr Walsh had been chief executive since July 2014 and had brought the chamber through a difficult period. He was appointed following the controversial departure of previous chief executive Roger Gordon.
"During his time in the role he has led the chamber back to financial and membership stability, after a period of uncertainty.
"The board of the chamber wishes to express their appreciation of Darrin's work and wish him well in his new role. "
Mr McRae said an interim chief executive was expected to be announced next week.
"We're not going to rush to appoint someone [permanently]. We'll take our time making sure we get the right person because it's such an important role."
He said the chamber was in a "good place" and he was "quietly confident" of finding a replacement with the skillset the job required.
Rotorua mayor Steve Chadwick said the Rotorua Lakes Council had built up a good relationship with the chamber under Mr Walsh.
"I got to know Darrin as more of a friend in Dancing With the Stars and when he gets the bit between his teeth he really goes for it, I'm sure he'll add to the credit union's success."
Credit Union Central general manager Gavin Long said he was pleased Mr Walsh had accepted his offer.
"It's awesome to be able to kick off a new product offering with Darrin at the helm."
Mr Long said the credit union did not lend to limited liability companies, "we lend to small businesses like smaller mum and pop businesses, which is what he's going to be doing, a helping businesses from scratch".
"It will take guts and skill, and Darrin is the man for it."