The Duke of Cambridge return to work as a pilot with the East Anglian Air Ambulance after taking a break ahead of the birth of Princess Charlotte.
He having taken unpaid leave in April before Princess Charlotte was born on 2 May.
The family has been at their home on the Sandringham estate in Norfolk.
Prince William is understood to be in the closing stages of his pilot training with the ambulance team.
He will transport patients to hospital once his training is complete.
The Duke of Cambridge previously served in the Royal Air Force, most recently as a search and rescue pilot.
He has had several official engagements since the birth of his second child, including awarding actress Sheridan Smith an OBE.
The charity East Anglian Air Ambulance, which has bases in Norwich and Cambridge, ordered a new £1.7m helicopter four years ago.
It came into service in Cambridge in April and is set to be flown by Prince William.
The air ambulance attends emergencies across Bedfordshire, Cambridgeshire, Norfolk and Suffolk reports BBC.