Chief Justice of Rajasthan High Court Sunil Ambwani administered the oath of office to Singh at a ceremony held at Raj Bhawan here.
Before that, Chief Secretary Rajiv Mehirshi read out the warrant of appointment issued by the President. Assembly Speaker Kailash Meghwal, Chief Minister Vasundhara Raje and senior officers were present on the occasion.
Enthusiast party workers shouted slogans 'jai shree ram' and 'vande matram' when Singh was taking the oath. He was also given a guard of honour.
U P Governor Ram Naik was holding the additional charge of Rajasthan before the appointment of Kalyan Singh.
Naik was given the additional charge of Rajasthan after Margaret Alva completed her term on August 5.