"It is with great reluctance and disappointment that I announce my retirement from concert touring. I have been so honored to bring my shows to the public for the past 50 years," said Diamond in a statement.
"My sincerest apologies to everyone who purchased tickets and were planning to come to the upcoming shows. I plan to remain active in writing, recording and other projects for a long time to come.
"My thanks goes out to my loyal and devoted audiences around the world. You will always have my appreciation for your support and encouragement. This ride has been 'so good, so good, so good' thanks to you."
Diamond (76) had been due to perform in Christchurch on March 15 and the Mission show in Napier on March 17 as part of his 50th Anniversary tour.
A press release issued today said "the onset of the disease has made it difficult to travel and perform on a large scale basis".
Promoter Paul Dainty said he was "devastated" at the news.
"I am devastated and saddened to hear the news of Neil's illness and his retirement from touring. I have had the honour of promoting Neil's numerous tours in Australia and New Zealand, he is one of the world's greatest artists and we and his thousands and thousands of fans here will miss seeing him tour down under."
Full refunds are available for his shows.
