"We are going to win all 11 seats," said Deputy Chief Minister Keshav Maurya.
The BJP is contesting 10 seats, having left one (Pratapgarh) for its ally Apna Dal.
The party has an edge in the by-elections that have witnessed a four-cornered contest.
For the Samajwadi Party and the Bahujan Samaj Party, the results were a matter of prestige. Both the parties held one seat each and retaining their constituencies was a major challenge for them.
The Congress has nothing to lose in the by-elections since it did not have even a single seat where by-elections were held.
The by-elections were held in Gangoh, Rampur, Iglas (SC), Lucknow Cantonment, Govind Nagar, Manikpur, Pratapgarh, Zaidpur (SC), Jalalpur, Balha (SC), and Ghosi.
According to the state's Chief Electoral Officer, as many as 109 candidates are in fray.
The maximum number of candidates (13) are from Lucknow Cantonment and the Jalalpur Assembly constituencies, followed by 11 each in Ghosi, Gangoh, Pratapgarh, and Balha. Nine candidates each are in the fray in Govind Nagar and Manikpur, while seven candidates are contesting from Rampur, Iglas and Zaidpur.
The by-elections were necessitated after the legislators were elected to the Lok Sabha and one member, Phagu Chauhan, resigned after he was appointed Governor of Bihar.
( With inputs from IANS )