West Bengal Governor Jagdeep Dhankhar administered the oath of office to three newly-elected MLAs, including Chief Minister Mamata Banerjee, at the state Assembly on Thursday.
Besides Banerjee, Amirul Islam and Jakir Hossain also took oath as MLAs.
In the recently concluded by-polls, Mamata Banerjee won from Bhawanipore with a margin of over 58,000 votes.
According to the Election Commission of India, Banerjee got 85,263 votes which are around 71.90 per cent of the total votes in the by-elections.
BJP candidate Priyanka Tibrewal got 26,428 votes and Communist Party of India (CPI) candidate Srijib Biswas secured 4,226 votes.
Jakir Hossain was elected from Jangipur and Amirul Islam was elected from Samserganj assembly seats in West Bengal.