Community Services Minister Joanne Bernard says the move is meant to address a gap, because currently, protections are only provided to children up to the age of 16, albeit in they are mandatory in those cases.
Amendments to the Children and Family Services Act would also broaden the definition of abuse and neglect to include emotional abuse.
Bernard says the changes are aimed at offering better protection and support to vulnerable children and their families.
Department officials say the extension of protection to youth up to 19 years of age could see an additional 100 cases added to the child protection system.
Department statistics for 2014-15 show that 1,200 children came under supervision orders while 460 were taken into temporary care and 114 required permanent care.
Bernard says the changes will not be passed until the fall to allow for consultation.