A 20-year-old woman from Madagascar, suspected of giving birth on the flight, was arrested.
The Air Mauritius Plane, which arrived from Madagascar, landed at Sir Seewoosagur Ramgoolam International Airport on 1 January.
Airport officers discovered when they screened the plane for a routine customs check. They rushed the baby back to a public hospital for further treatment.
The woman was suspected of being the child's mother, who had initially denied the boy was her child, and she was made to undergo the medical examination, which confirmed that she had just given birth to the child.
She was placed under police surveillance at the hospital.
Both the baby and mother are said to be healthy and stable.
The Malagasy woman who arrived in Mauritius on a two-year work permit will be questioned after her release from the hospital and will be charged with abandoning a newborn infant.
(With help from Agencies.)