The 41-year-old leader, who won Tonk assembly constituency in the recently concluded assembly elections, had pledged in 2014 to not wear the traditional turban till the party returns to power in the state.
The Congress had faced defeat in 2013 assembly polls in the state.
Mr Pilot had been a former Lok Sabha lawmaker from Dausa and Ajmer.
On Monday, senior Congress leader Ashok Gehlot was sworn in as the chief minister of Rajasthan, while Mr Pilot took oath as his deputy.
Governor Kalyan Singh administered the oath of office to Mr Gehlot and Mr Pilot in the presence of Congress president Rahul Gandhi and former prime minister Manmohan Singh at Jaipur’s Albert Hall