Senior Congress leader and Puducherry chief minister V Narayanasamy won the bypoll to the Nellithope assembly constituency defeating AIADMK's Om Sakthi Segar, by a margin of 11,144 votes.
While Narayanasamy, whose victory was on expected lines, polled 18,709 votes out of the total 26,564 votes, Segar got 7,565 votes.
A John Kumar of the Congress had vacated the seat to enable Narayanasamy, who is not a member of the assembly, contest a by-election before December 6 deadline for getting elected to the House.
Narayanasamy was accorded a tumultuous reception by volunteers of Congress and DMK, its alliance partner in the assembly.
Speaking to reporters outside the counting centre, he said he was grateful to the workers and functionaries of the Congress and DMK and its president M Karunanidhi and its treasurer MK Stalin.
Thanking the people of Nellithope for supporting him in the bypoll, Narayanasamy asserted that he would ensure that Puducherry developed into a model state.
"I will spare no efforts to ensure that unemployment problem of the youth in the constituency is expeditiously tackled."
Congress cadres burst crackers at various places to celebrate the victory of Narayanasamy. Congress has a strength of 15 while its ally DMK two in the 30-member assembly.
69-year-old Narayanasamy, who had served as minister of state in the Prime Minister's Office in the second UPA government after serving as MoS parliamentary affairs in UPA-I, was sworn in as chief minister on June 6.
A law graduate, Narayanasamy practised law for more than ten years since 1973 and jumped into active politics in 1985. He was elected for the first time to Rajya Sabha and retained the seat in 1991. However, he was defeated in the contest for the RS seat in 1997 by DMK and regained the seat in 2003. He was the PCC president in 2007.