The air ambulance pilot took unpaid leave in April following the first phase of his training with East Anglian Air Ambulance.
The Duchess Of Cambridge gave birth to Princess Charlotte on 2 May and since then the family have been spending time at their home, Anmer Hall, on the Sandringham estate in Norfolk.
The Georgian country home was given to the couple by the Queen as a wedding present.
William is understood to be in the closing stages of his training to be a pilot with the ambulance team, after which he will transport patients to hospital.
He previously served in the Royal Air Force, most recently as a search and rescue pilot.
Prince William has had several official engagements since the birth of his second child, including awarding actress Sheridan Smith an OBE.
And the Duke, an Aston Villa supporter and president of the FA, watched his club endure a crushing 4-0 defeat at the hands on Arsenal in the Wembley clash on Saturday 30 May.
His return tomorrow marks the end of a break of almost six weeks from his flying duties.