McCullum said he wears a daffodil to support all Kiwis affected by cancer.
"Everyone has their own stories, but I wear it for all of New Zealand. One in three New Zealanders is touched by cancer. It's such a huge issue in New Zealand."
McCullum was standing with ANZ staffers who spent time collecting donations, organising bake sales and other events to support Daffodil Day.
"It's definitely been a busy morning... the way ANZ gets behind it is unbelievable.
"There's a great awareness for Daffodil Day, everyone in New Zealand understands it."
McCullum hopes the ANZ International Series over the summer months gets the same amount of awareness from the public.
"I think we will get a lot of support," he said.
"We've got a big year coming up, I'm hopeful we will perform."
ANZ hopes to fundraise $1 million for the Cancer Society this Daffodil Day, which marks the 25th anniversary of the nationwide charity fundraiser. Last year's total came in at just over $1 million.
• Daffodil Day is Friday, August 28. To donate visit the Daffodil Day website.