The counting begins at 10 a.m. at the Congress headquarters in Delhi, where sealed ballot boxes from around the country have been transported.
According to the Congress, approximately 96% of the 9,915 eligible leaders voted in the election held on Monday.
Mallikarjun Kharge, a long-time Gandhi family supporter, is widely regarded as the race's frontrunner.
However, this has supplied fodder to critics who claim that if he wins, the Gandhis will be able to govern the party remotely.
Mr. Kharge and Mr. Tharoor have both stated that the Gandhis are uninvolved in the election.
Mr Tharoor, on the other hand, has stated that the "odds were stacked against us because the party officials and establishment were heavily behind the other candidate."
Sonia Gandhi agreed to temporarily lead the party after Rahul Gandhi stood down three years ago, taking responsibility for the party's two straight routs in the 2014 and 2019 national elections.