Patil was administered the oath of office by seniormost judge of Calcutta High Court Justice A K Banerjee.
Chief Minister Mamata Banerjee was present on the occasion this evening at the majestic Raj Bhavan here along with senior colleagues in her Cabinet.
Speaker Biman Banerjee, leader of Opposition Surjyakanta Mishra and several diplomats were also present.
The chief minister exchanged pleasantries with the new Governor and presented him with a flower bouquet following the brief ceremony.
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Talking to reporters later, Banerjee said "I know him (Patil) for long, nice that he has come. Swagatam."
Earlier in the day, M K Narayanan demitted office and left for Chennai along with his wife Padmini.
Narayanan was given a guard of honour by the Kolkata Police's Mounted Police Division. He had taken over as West Bengal's 24th Governor on January 24, 2010.
Narayanan's resignation as West Bengal Governor was accepted by President Pranab Mukherjee yesterday and Bihar Governor D Y Patil was asked to hold additional charge of the post as interim arrangement.
Eighty-year-old Narayanan was recently questioned by CBI as a "witness" in the AgustaWestland VVIP helicopter deal probe.
Besides Narayanan, Nagaland Governor Ashwani Kumar, Uttar Pradesh Governor B L Joshi and Chhattisgarh Governor Shekhar Dutt have put in their papers since the new government took over at the Centre.