CYF acting southern regional director Theresa Perham said the child had been placed with a Child, Youth and Family caregiver "until we could ensure his safety with family''
"He is doing well,'' she said.
"We are working closely with the family to make arrangements for the future care of this little boy.''
Babies and young children should never be left without adequate supervision, she said.
"We would advise anyone who comes across a baby in this situation to call the police.
"When we are alerted to children being left unsupervised, we ensure the immediate safety of the children and work with the parents and wider family to ensure the children are adequately supervised in the future.''
The Christchurch case came just days after a baby was left locked in a car outside a Porirua supermarket, with a note saying its mother was inside and to call a mobile number if there were any issues.
Police and CYF are trying to track down that mother.
