The girl was found was found early yesterday afternoon by a driver of an InterCity bus from Whangārei to Auckland.
A 27-year-old woman has been charged with ill-treatment of a child and appeared in North Shore District Court today.
The child had been in the suitcase for nearly an hour wearing only a nappy, RNZ understands.
Detective Inspector Simon Harrison said police were called at 12.50pm, after a passenger asked for access to the luggage compartment during a planned stop in Kaiwaka, Northland.
Detective Inspector Simon Harrison said the driver became concerned when he noticed the bag moving.
"When the driver opened the suitcase, they discovered the two-year-old girl."
RNZ understands the girl had been on the bus for nearly an hour and when taken out of the suitcase she was only wearing a nappy.
Harrison said the little girl was reported to be "very hot", but otherwise unharmed.
She has been taken to hospital in a "minor" condition for an extensive medical assessment.
The woman who has been charged was due to appear in North Shore District Court today.
"We would like to acknowledge and commend the bus driver, who noticed something wasn't right and took immediate action, preventing what could have been a far worse outcome," Harrison said.
"Police inquiries into this incident are ongoing and further charges cannot be ruled out. Oranga Tamariki [the Ministry for Children] has also been notified."
An Intercity spokesperson said the company was aware of an incident involving a passenger on one of its services earlier yesterday.
"Police were called to respond, and they are now investigating the matter. No one was harmed during the incident and the service has resumed.
"As this is now an active police investigation, we are unable to comment further."
Oranga Tamariki (the Ministry for Children) said it was working with the child's family to ensure they were safe.
