Voters queued up to exercise their franchise from early in the day in the by-election. Fifteen candidates are in the fray.
The main contest is between the ruling Shiromani Akali Dal and the Congress. The Aam Aadmi Party (AAP), which won four seats in the Lok Sabha battle in Punjab, is also in the fray.
Former union minister of state for external affairs Preneet Kaur is contesting in Patiala. The seat was vacated by her husband and former chief minister Amarinder Singh after he was elected to the Lok Sabha from Amritsar in May.
Preneet Kaur has been a three-time Lok Sabha MP from Patiala. She lost the Lok Sabha election this year to Dharamvira Gandhi of the AAP.
Amarinder Singh is now the deputy leader of the Congress in the Lok Sabha.
He had defeated BJP leader Arun Jaitley, now the union finance and defence minister, in a bitter contest for the Amritsar Lok Sabha seat by over one lakh votes.
The by-poll in Talwandi Sabo is being held as Congress legislator Jeet Mohinder Singh quit the party and joined the Akali Dal.
The Akali Dal has named Jeet Mohinder Singh as its candidate for the Talwandi Sabo seat in Bathinda district. He is pitted against Harminder Singh Jassi of the Congress.
Counting of votes will take place Aug 25.