The newly launched Oranga Tamariki - the Ministry for Vulnerable Children - is set to be under "constant restructure" for the next few years.
CYF has been under review almost continuously since its inception in 1989 and has been restructured 14 times.
Today is the Ministry's first day of operation.
Children's Minister Anne Tolley said she had questioned the ministry's chief executive Grainne Moss when she saw the ministry had been designed with nine deputy executives, but she had been assured it was only to get the ministry up and running and that number would be reduced.
"I think there will be a constant restructure, you will see a great many changes over the next four to five years.
"We've lifted and shifted to start with."
She said about 5000 children were in care at the moment, and almost 10,000 more were being worked with, so it was important to make sure that work could continue smoothly.
"We want to continue that work whilst we're redesigning the way that we're going to work in the future."
Ms Moss said changing the care and protection system would be a four or five year process.
She said the shift from being an agency that responds to a crisis, to one that focuses on prevention and early intervention, was significant, would take time, and would need buy-in from people outside the ministry.
"It's about not just far-reaching change within Oranga Tamariki, it's about far-reaching change across the whole system that supports children including the community."
While the sign on the building hasn't been replaced yet, the social workers inside Oranga Tamariki's national contact centre in Auckland were no longer saying they were from Child, Youth and Family when they were answering and making calls.
Greg Versalko, the ministry's acting deputy chief executive for care, said one of the first calls into the centre in the early hours this morning was from a young person asking how the changes will affect them.
He said they've spent a lot of time training staff about what the changes mean and how it impacts the services they offer.
"Every social worker understands that this about better services to young people and they're very excited about that," he said.
"It's why they do their jobs, it's why they do statutory social work. We can't make decisions for young people without them being involved. It's as simple as that."